Class Calendar

java.lang.Object
com.ibm.icu.util.Calendar
All Implemented Interfaces:
Serializable, Cloneable, Comparable<Calendar>
Direct Known Subclasses:
ChineseCalendar, CopticCalendar, EthiopicCalendar, GregorianCalendar, HebrewCalendar, IndianCalendar, IslamicCalendar, PersianCalendar

public abstract class Calendar extends Object implements Serializable, Cloneable, Comparable<Calendar>
.

Calendar is an abstract base class for converting between a Date object and a set of integer fields such as YEAR, MONTH, DAY, HOUR, and so on. (A Date object represents a specific instant in time with millisecond precision. See Date for information about the Date class.)

Subclasses of Calendar interpret a Date according to the rules of a specific calendar system. ICU4J contains several subclasses implementing different international calendar systems.

Like other locale-sensitive classes, Calendar provides a class method, getInstance, for getting a generally useful object of this type. Calendar's getInstance method returns a calendar of a type appropriate to the locale, whose time fields have been initialized with the current date and time:

Calendar rightNow = Calendar.getInstance()

When a ULocale is used by getInstance, its 'calendar' tag and value are retrieved if present. If a recognized value is supplied, a calendar is provided and configured as appropriate. Currently recognized tags are "buddhist", "chinese", "coptic", "ethiopic", "gregorian", "hebrew", "islamic", "islamic-civil", "japanese", and "roc". For example:

Calendar cal = Calendar.getInstance(new ULocale("en_US@calendar=japanese"));
will return an instance of JapaneseCalendar (using en_US conventions for minimum days in first week, start day of week, et cetera).

A Calendar object can produce all the time field values needed to implement the date-time formatting for a particular language and calendar style (for example, Japanese-Gregorian, Japanese-Traditional). Calendar defines the range of values returned by certain fields, as well as their meaning. For example, the first month of the year has value MONTH == JANUARY for all calendars. Other values are defined by the concrete subclass, such as ERA and YEAR. See individual field documentation and subclass documentation for details.

When a Calendar is lenient, it accepts a wider range of field values than it produces. For example, a lenient GregorianCalendar interprets MONTH == JANUARY, DAY_OF_MONTH == 32 as February 1. A non-lenient GregorianCalendar throws an exception when given out-of-range field settings. When calendars recompute field values for return by get(), they normalize them. For example, a GregorianCalendar always produces DAY_OF_MONTH values between 1 and the length of the month.

Calendar defines a locale-specific seven day week using two parameters: the first day of the week and the minimal days in first week (from 1 to 7). These numbers are taken from the locale resource data when a Calendar is constructed. They may also be specified explicitly through the API.

When setting or getting the WEEK_OF_MONTH or WEEK_OF_YEAR fields, Calendar must determine the first week of the month or year as a reference point. The first week of a month or year is defined as the earliest seven day period beginning on getFirstDayOfWeek() and containing at least getMinimalDaysInFirstWeek() days of that month or year. Weeks numbered ..., -1, 0 precede the first week; weeks numbered 2, 3,... follow it. Note that the normalized numbering returned by get() may be different. For example, a specific Calendar subclass may designate the week before week 1 of a year as week n of the previous year.

When computing a Date from time fields, some special circumstances may arise: there may be insufficient information to compute the Date (such as only year and month but no day in the month), there may be inconsistent information (such as "Tuesday, July 15, 1996" -- July 15, 1996 is actually a Monday), or the input time might be ambiguous because of time zone transition.

Insufficient information. The calendar will use default information to specify the missing fields. This may vary by calendar; for the Gregorian calendar, the default for a field is the same as that of the start of the epoch: i.e., YEAR = 1970, MONTH = JANUARY, DATE = 1, etc.

Inconsistent information. If fields conflict, the calendar will give preference to fields set more recently. For example, when determining the day, the calendar will look for one of the following combinations of fields. The most recent combination, as determined by the most recently set single field, will be used.

 MONTH + DAY_OF_MONTH
 MONTH + WEEK_OF_MONTH + DAY_OF_WEEK
 MONTH + DAY_OF_WEEK_IN_MONTH + DAY_OF_WEEK
 DAY_OF_YEAR
 DAY_OF_WEEK + WEEK_OF_YEAR
For the time of day:
 HOUR_OF_DAY
 AM_PM + HOUR

Ambiguous Wall Clock Time. When time offset from UTC has changed, it produces an ambiguous time slot around the transition. For example, many US locations observe daylight saving time. On the date switching to daylight saving time in US, wall clock time jumps from 12:59 AM (standard) to 2:00 AM (daylight). Therefore, wall clock time from 1:00 AM to 1:59 AM do not exist on the date. When the input wall time fall into this missing time slot, the ICU Calendar resolves the time using the UTC offset before the transition by default. In this example, 1:30 AM is interpreted as 1:30 AM standard time (non-exist), so the final result will be 2:30 AM daylight time.

On the date switching back to standard time, wall clock time is moved back one hour at 2:00 AM. So wall clock time from 1:00 AM to 1:59 AM occur twice. In this case, the ICU Calendar resolves the time using the UTC offset after the transition by default. For example, 1:30 AM on the date is resolved as 1:30 AM standard time.

Ambiguous wall clock time resolution behaviors can be customized by Calendar APIs setRepeatedWallTimeOption(int) and setSkippedWallTimeOption(int). These methods are available in ICU 49 or later versions.

Note: for some non-Gregorian calendars, different fields may be necessary for complete disambiguation. For example, a full specification of the historial Arabic astronomical calendar requires year, month, day-of-month and day-of-week in some cases.

Note: There are certain possible ambiguities in interpretation of certain singular times, which are resolved in the following ways:

  1. 24:00:00 "belongs" to the following day. That is, 23:59 on Dec 31, 1969 < 24:00 on Jan 1, 1970 < 24:01:00 on Jan 1, 1970
  2. Although historically not precise, midnight also belongs to "am", and noon belongs to "pm", so on the same day, 12:00 am (midnight) < 12:01 am, and 12:00 pm (noon) < 12:01 pm

The date or time format strings are not part of the definition of a calendar, as those must be modifiable or overridable by the user at runtime. Use DateFormat to format dates.

Field manipulation methods

Calendar fields can be changed using three methods: set(), add(), and roll().

set(f, value) changes field f to value. In addition, it sets an internal member variable to indicate that field f has been changed. Although field f is changed immediately, the calendar's milliseconds is not recomputed until the next call to get(), getTime(), or getTimeInMillis() is made. Thus, multiple calls to set() do not trigger multiple, unnecessary computations. As a result of changing a field using set(), other fields may also change, depending on the field, the field value, and the calendar system. In addition, get(f) will not necessarily return value after the fields have been recomputed. The specifics are determined by the concrete calendar class.

Example: Consider a GregorianCalendar originally set to August 31, 1999. Calling set(Calendar.MONTH, Calendar.SEPTEMBER) sets the calendar to September 31, 1999. This is a temporary internal representation that resolves to October 1, 1999 if getTime()is then called. However, a call to set(Calendar.DAY_OF_MONTH, 30) before the call to getTime() sets the calendar to September 30, 1999, since no recomputation occurs after set() itself.

add(f, delta) adds delta to field f. This is equivalent to calling set(f, get(f) + delta) with two adjustments:

Add rule 1. The value of field f after the call minus the value of field f before the call is delta, modulo any overflow that has occurred in field f. Overflow occurs when a field value exceeds its range and, as a result, the next larger field is incremented or decremented and the field value is adjusted back into its range.

Add rule 2. If a smaller field is expected to be invariant, but   it is impossible for it to be equal to its prior value because of changes in its minimum or maximum after field f is changed, then its value is adjusted to be as close as possible to its expected value. A smaller field represents a smaller unit of time. HOUR is a smaller field than DAY_OF_MONTH. No adjustment is made to smaller fields that are not expected to be invariant. The calendar system determines what fields are expected to be invariant.

In addition, unlike set(), add() forces an immediate recomputation of the calendar's milliseconds and all fields.

Example: Consider a GregorianCalendar originally set to August 31, 1999. Calling add(Calendar.MONTH, 13) sets the calendar to September 30, 2000. Add rule 1 sets the MONTH field to September, since adding 13 months to August gives September of the next year. Since DAY_OF_MONTH cannot be 31 in September in a GregorianCalendar, add rule 2 sets the DAY_OF_MONTH to 30, the closest possible value. Although it is a smaller field, DAY_OF_WEEK is not adjusted by rule 2, since it is expected to change when the month changes in a GregorianCalendar.

roll(f, delta) adds delta to field f without changing larger fields. This is equivalent to calling add(f, delta) with the following adjustment:

Roll rule. Larger fields are unchanged after the call. A larger field represents a larger unit of time. DAY_OF_MONTH is a larger field than HOUR.

Example: Consider a GregorianCalendar originally set to August 31, 1999. Calling roll(Calendar.MONTH, 8) sets the calendar to April 30, 1999. Add rule 1 sets the MONTH field to April. Using a GregorianCalendar, the DAY_OF_MONTH cannot be 31 in the month April. Add rule 2 sets it to the closest possible value, 30. Finally, the roll rule maintains the YEAR field value of 1999.

Example: Consider a GregorianCalendar originally set to Sunday June 6, 1999. Calling roll(Calendar.WEEK_OF_MONTH, -1) sets the calendar to Tuesday June 1, 1999, whereas calling add(Calendar.WEEK_OF_MONTH, -1) sets the calendar to Sunday May 30, 1999. This is because the roll rule imposes an additional constraint: The MONTH must not change when the WEEK_OF_MONTH is rolled. Taken together with add rule 1, the resultant date must be between Tuesday June 1 and Saturday June 5. According to add rule 2, the DAY_OF_WEEK, an invariant when changing the WEEK_OF_MONTH, is set to Tuesday, the closest possible value to Sunday (where Sunday is the first day of the week).

Usage model. To motivate the behavior of add() and roll(), consider a user interface component with increment and decrement buttons for the month, day, and year, and an underlying GregorianCalendar. If the interface reads January 31, 1999 and the user presses the month increment button, what should it read? If the underlying implementation uses set(), it might read March 3, 1999. A better result would be February 28, 1999. Furthermore, if the user presses the month increment button again, it should read March 31, 1999, not March 28, 1999. By saving the original date and using either add() or roll(), depending on whether larger fields should be affected, the user interface can behave as most users will intuitively expect.

Note: You should always use roll and add rather than attempting to perform arithmetic operations directly on the fields of a Calendar. It is quite possible for Calendar subclasses to have fields with non-linear behavior, for example missing months or days during non-leap years. The subclasses' add and roll methods will take this into account, while simple arithmetic manipulations may give invalid results.

Calendar Architecture in ICU4J

Recently the implementation of Calendar has changed significantly in order to better support subclassing. The original Calendar class was designed to support subclassing, but it had only one implemented subclass, GregorianCalendar. With the implementation of several new calendar subclasses, including the BuddhistCalendar, ChineseCalendar, HebrewCalendar, IslamicCalendar, and JapaneseCalendar, the subclassing API has been reworked thoroughly. This section details the new subclassing API and other ways in which com.ibm.icu.util.Calendar differs from java.util.Calendar.

Changes

Overview of changes between the classic Calendar architecture and the new architecture.

  • The fields[] array is private now instead of protected. Subclasses must access it using the methods internalSet(int, int) and internalGet(int). Motivation: Subclasses should not directly access data members.
  • The time long word is private now instead of protected. Subclasses may access it using the method internalGetTimeInMillis(), which does not provoke an update. Motivation: Subclasses should not directly access data members.
  • The scope of responsibility of subclasses has been drastically reduced. As much functionality as possible is implemented in the Calendar base class. As a result, it is much easier to subclass Calendar. Motivation: Subclasses should not have to reimplement common code. Certain behaviors are common across calendar systems: The definition and behavior of week-related fields and time fields, the arithmetic (add and roll) behavior of many fields, and the field validation system.
  • The subclassing API has been completely redesigned.
  • The Calendar base class contains some Gregorian calendar algorithmic support that subclasses can use (specifically in handleComputeFields(int)). Subclasses can use the methods getGregorianXxx() to obtain precomputed values. Motivation: This is required by all Calendar subclasses in order to implement consistent time zone behavior, and Gregorian-derived systems can use the already computed data.
  • The FIELD_COUNT constant has been removed. Use getFieldCount(). In addition, framework API has been added to allow subclasses to define additional fields. Motivation: The number of fields is not constant across calendar systems.
  • The range of handled dates has been narrowed from +/- ~300,000,000 years to +/- ~5,000,000 years. In practical terms this should not affect clients. However, it does mean that client code cannot be guaranteed well-behaved results with dates such as Date(Long.MIN_VALUE) or Date(Long.MAX_VALUE). Instead, the Calendar protected constants should be used. Motivation: With the addition of the JULIAN_DAY field, Julian day numbers must be restricted to a 32-bit int. This restricts the overall supported range. Furthermore, restricting the supported range simplifies the computations by removing special case code that was used to accommodate arithmetic overflow at millis near Long.MIN_VALUE and Long.MAX_VALUE.
  • New fields are implemented: JULIAN_DAY defines single-field specification of the date. MILLISECONDS_IN_DAY defines a single-field specification of the wall time. DOW_LOCAL and YEAR_WOY implement localized day-of-week and week-of-year behavior.
  • Subclasses can access protected millisecond constants defined in Calendar.
  • New API has been added to support calendar-specific subclasses of DateFormat.
  • Several subclasses have been implemented, representing various international calendar systems.

Subclass API

The original Calendar API was based on the experience of implementing a only a single subclass, GregorianCalendar. As a result, all of the subclassing kinks had not been worked out. The new subclassing API has been refined based on several implemented subclasses. This includes methods that must be overridden and methods for subclasses to call. Subclasses no longer have direct access to fields and stamp. Instead, they have new API to access these. Subclasses are able to allocate the fields array through a protected framework method; this allows subclasses to specify additional fields.

More functionality has been moved into the base class. The base class now contains much of the computational machinery to support the Gregorian calendar. This is based on two things: (1) Many calendars are based on the Gregorian calendar (such as the Buddhist and Japanese imperial calendars). (2) All calendars require basic Gregorian support in order to handle timezone computations.

Common computations have been moved into Calendar. Subclasses no longer compute the week related fields and the time related fields. These are commonly handled for all calendars by the base class.

Subclass computation of time => fields

The ERA, YEAR, EXTENDED_YEAR, MONTH, DAY_OF_MONTH, and DAY_OF_YEAR fields are computed by the subclass, based on the Julian day. All other fields are computed by Calendar.

  • Subclasses should implement handleComputeFields(int) to compute the ERA, YEAR, EXTENDED_YEAR, MONTH, DAY_OF_MONTH, and DAY_OF_YEAR fields, based on the value of the JULIAN_DAY field. If there are calendar-specific fields not defined by Calendar, they must also be computed. These are the only fields that the subclass should compute. All other fields are computed by the base class, so time and week fields behave in a consistent way across all calendars. The default version of this method in Calendar implements a proleptic Gregorian calendar. Within this method, subclasses may call getGregorianXxx() to obtain the Gregorian calendar month, day of month, and extended year for the given date.

Subclass computation of fields => time

The interpretation of most field values is handled entirely by Calendar. Calendar determines which fields are set, which are not, which are set more recently, and so on. In addition, Calendar handles the computation of the time from the time fields and handles the week-related fields. The only thing the subclass must do is determine the extended year, based on the year fields, and then, given an extended year and a month, it must return a Julian day number.

  • Subclasses should implement handleGetExtendedYear() to return the extended year for this calendar system, based on the YEAR, EXTENDED_YEAR, and any fields that the calendar system uses that are larger than a year, such as ERA.
  • Subclasses should implement handleComputeMonthStart(int, int, boolean) to return the Julian day number associated with a month and extended year. This is the Julian day number of the day before the first day of the month. The month number is zero-based. This computation should not depend on any field values.

Other methods

  • Subclasses should implement handleGetMonthLength(int, int) to return the number of days in a given month of a given extended year. The month number, as always, is zero-based.
  • Subclasses should implement handleGetYearLength(int) to return the number of days in the given extended year. This method is used by computeWeekFields to compute the WEEK_OF_YEAR and YEAR_WOY fields.
  • Subclasses should implement handleGetLimit(int, int) to return the protected values of a field, depending on the value of limitType. This method only needs to handle the fields ERA, YEAR, MONTH, WEEK_OF_YEAR, WEEK_OF_MONTH, DAY_OF_MONTH, DAY_OF_YEAR, DAY_OF_WEEK_IN_MONTH, YEAR_WOY, and EXTENDED_YEAR. Other fields are invariant (with respect to calendar system) and are handled by the base class.
  • Optionally, subclasses may override validateField(int) to check any subclass-specific fields. If the field's value is out of range, the method should throw an IllegalArgumentException. The method may call super.validateField(field) to handle fields in a generic way, that is, to compare them to the range getMinimum(field)..getMaximum(field).
  • Optionally, subclasses may override handleCreateFields() to create an int[] array large enough to hold the calendar's fields. This is only necessary if the calendar defines additional fields beyond those defined by Calendar. The length of the result must be be between the base and maximum field counts.
  • Optionally, subclasses may override handleGetDateFormat(java.lang.String, java.util.Locale) to create a DateFormat appropriate to this calendar. This is only required if a calendar subclass redefines the use of a field (for example, changes the ERA field from a symbolic field to a numeric one) or defines an additional field.
  • Optionally, subclasses may override roll and add to handle fields that are discontinuous. For example, in the Hebrew calendar the month "Adar I" only occurs in leap years; in other years the calendar jumps from Shevat (month #4) to Adar (month #6). The HebrewCalendar.add and HebrewCalendar.roll methods take this into account, so that adding 1 month to Shevat gives the proper result (Adar) in a non-leap year. The protected utility method pinField is often useful when implementing these two methods.

Normalized behavior

The behavior of certain fields has been made consistent across all calendar systems and implemented in Calendar.

  • Time is normalized. Even though some calendar systems transition between days at sunset or at other times, all ICU4J calendars transition between days at local zone midnight. This allows ICU4J to centralize the time computations in Calendar and to maintain basic correspondences between calendar systems. Affected fields: AM_PM, HOUR, HOUR_OF_DAY, MINUTE, SECOND, MILLISECOND, ZONE_OFFSET, and DST_OFFSET.
  • DST behavior is normalized. Daylight savings time behavior is computed the same for all calendar systems, and depends on the value of several GregorianCalendar fields: the YEAR, MONTH, and DAY_OF_MONTH. As a result, Calendar always computes these fields, even for non-Gregorian calendar systems. These fields are available to subclasses.
  • Weeks are normalized. Although locales define the week differently, in terms of the day on which it starts, and the designation of week number one of a month or year, they all use a common mechanism. Furthermore, the day of the week has a simple and consistent definition throughout history. For example, although the Gregorian calendar introduced a discontinuity when first instituted, the day of week was not disrupted. For this reason, the fields DAY_OF_WEEK, WEEK_OF_YEAR, WEEK_OF_MONTH, DAY_OF_WEEK_IN_MONTH, DOW_LOCAL, YEAR_WOY are all computed in a consistent way in the base class, based on the EXTENDED_YEAR, DAY_OF_YEAR, MONTH, and DAY_OF_MONTH, which are computed by the subclass.

Supported range

The allowable range of Calendar has been narrowed. GregorianCalendar used to attempt to support the range of dates with millisecond values from Long.MIN_VALUE to Long.MAX_VALUE. This introduced awkward constructions (hacks) which slowed down performance. It also introduced non-uniform behavior at the boundaries. The new Calendar protocol specifies the maximum range of supportable dates as those having Julian day numbers of -0x7F000000 to +0x7F000000. This corresponds to years from ~5,800,000 BCE to ~5,800,000 CE. Programmers should use the protected constants in Calendar to specify an extremely early or extremely late date.

General notes

  • Calendars implementations are proleptic. For example, even though the Gregorian calendar was not instituted until the 16th century, the GregorianCalendar class supports dates before the historical onset of the calendar by extending the calendar system backward in time. Similarly, the HebrewCalendar extends backward before the start of its epoch into zero and negative years. Subclasses do not throw exceptions because a date precedes the historical start of a calendar system. Instead, they implement handleGetLimit(int, int) to return appropriate limits on YEAR, ERA, etc. fields. Then, if the calendar is set to not be lenient, out-of-range field values will trigger an exception.
  • Calendar system subclasses compute a extended year. This differs from the YEAR field in that it ranges over all integer values, including zero and negative values, and it encapsulates the information of the YEAR field and all larger fields. Thus, for the Gregorian calendar, the EXTENDED_YEAR is computed as ERA==AD ? YEAR : 1-YEAR. Another example is the Mayan long count, which has years (KUN) and nested cycles of years (KATUN and BAKTUN). The Mayan EXTENDED_YEAR is computed as TUN + 20 * (KATUN + 20 * BAKTUN). The Calendar base class uses the EXTENDED_YEAR field to compute the week-related fields.
Author:
Mark Davis, Deborah Goldsmith, Chen-Lieh Huang, Alan Liu, Laura Werner
See Also:
  • Nested Class Summary

    Nested Classes
    Modifier and Type
    Class
    Description
    static class 
    Deprecated.
    This API is ICU internal only.
    static final class 
    Simple, immutable struct-like class for access to the CLDR week data.
  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    static final int
    Value of the AM_PM field indicating the period of the day from midnight to just before noon.
    static final int
    Field number for get and set indicating whether the HOUR is before or after noon.
    static final int
    Value of the MONTH field indicating the fourth month of the year.
    static final int
    Value of the MONTH field indicating the eighth month of the year.
    protected static final int
    Deprecated.
    ICU 58 The numeric value may change over time, see ICU ticket #12420.
    static final int
    Field number for get and set indicating the day of the month.
    static final int
    Field number for get and set indicating the day of the month.
    static final int
    Field number for get and set indicating the day of the week.
    static final int
    Field number for get and set indicating the ordinal number of the day of the week within the current month.
    static final int
    Field number for get and set indicating the day number within the current year.
    static final int
    Value of the MONTH field indicating the twelfth month of the year.
    static final int
    Field number for get() and set() indicating the localized day of week.
    static final int
    Field number for get and set indicating the daylight savings offset in milliseconds.
    protected static final int
    The Julian day of the epoch, that is, January 1, 1970 on the Gregorian calendar.
    static final int
    Field number for get and set indicating the era, e.g., AD or BC in the Julian calendar.
    static final int
    Field number for get() and set() indicating the extended year.
    static final int
    Value of the MONTH field indicating the second month of the year.
    static final int
    Value of the DAY_OF_WEEK field indicating Friday.
    protected static final int
    Limit type for getLimit() and handleGetLimit() indicating the greatest minimum value that a field can take.
    static final int
    Field number for get and set indicating the hour of the morning or afternoon.
    static final int
    Field number for get and set indicating the hour of the day.
    protected static final int
    Value of the time stamp stamp[] indicating that a field has been set via computations from the time or from other fields.
    static final int
    Field indicating whether or not the current month is a leap month.
    protected static final int
    The Julian day of the Gregorian epoch, that is, January 1, 1 on the Gregorian calendar.
    static final int
    Value of the MONTH field indicating the first month of the year.
    static final int
    Field number for get() and set() indicating the modified Julian day number.
    static final int
    Value of the MONTH field indicating the seventh month of the year.
    static final int
    Value of the MONTH field indicating the sixth month of the year.
    protected static final int
    Limit type for getLimit() and handleGetLimit() indicating the least maximum value that a field can take.
    static final int
    Value of the MONTH field indicating the third month of the year.
    protected static final Date
    The maximum supported Date.
    protected static final int
    Deprecated.
    ICU 58 The numeric value may change over time, see ICU ticket #12420.
    protected static final int
    The maximum supported Julian day.
    protected static final long
    The maximum supported epoch milliseconds.
    protected static final int
    Limit type for getLimit() and handleGetLimit() indicating the maximum value that a field can take (greatest maximum).
    static final int
    Value of the MONTH field indicating the fifth month of the year.
    static final int
    Field number for get and set indicating the millisecond within the second.
    static final int
    Field number for get() and set() indicating the milliseconds in the day.
    protected static final Date
    The minimum supported Date.
    protected static final int
    The minimum supported Julian day.
    protected static final long
    The minimum supported epoch milliseconds.
    protected static final int
    Limit type for getLimit() and handleGetLimit() indicating the minimum value that a field can take (least minimum).
    protected static final int
    If the time stamp stamp[] has a value greater than or equal to MINIMUM_USER_SET then it has been set by the user via a call to set().
    static final int
    Field number for get and set indicating the minute within the hour.
    static final int
    Value of the DAY_OF_WEEK field indicating Monday.
    static final int
    Field number for get and set indicating the month.
    static final int
    Value of the MONTH field indicating the eleventh month of the year.
    static final int
    Value of the MONTH field indicating the tenth month of the year.
    protected static final long
    The number of milliseconds in one day.
    protected static final int
    The number of milliseconds in one hour.
    protected static final int
    The number of milliseconds in one minute.
    protected static final int
    The number of milliseconds in one second.
    protected static final long
    The number of milliseconds in one week.
    static final int
    Value of the AM_PM field indicating the period of the day from noon to just before midnight.
    protected static final int
    Value to OR against resolve table field values for remapping.
    static final int
    Value of the DAY_OF_WEEK field indicating Saturday.
    static final int
    Field number for get and set indicating the second within the minute.
    static final int
    Value of the MONTH field indicating the ninth month of the year.
    static final int
    Value of the DAY_OF_WEEK field indicating Sunday.
    static final int
    Value of the DAY_OF_WEEK field indicating Thursday.
    static final int
    Value of the DAY_OF_WEEK field indicating Tuesday.
    static final int
    Value of the MONTH field indicating the thirteenth month of the year.
    protected static final int
    Value of the time stamp stamp[] indicating that a field has not been set since the last call to clear().
    static final int
    Option used by setRepeatedWallTimeOption(int) and setSkippedWallTimeOption(int) specifying an ambiguous wall time to be interpreted as the earliest.
    static final int
    Option used by setRepeatedWallTimeOption(int) and setSkippedWallTimeOption(int) specifying an ambiguous wall time to be interpreted as the latest.
    static final int
    Option used by setSkippedWallTimeOption(int) specifying an ambiguous wall time to be interpreted as the next valid wall time.
    static final int
    Value of the DAY_OF_WEEK field indicating Wednesday.
    static final int
    Field number for get and set indicating the week number within the current month.
    static final int
    Field number for get and set indicating the week number within the current year.
    static final int
    static final int
    static final int
    static final int
    static final int
    Field number for get and set indicating the year.
    static final int
    Field number for get() and set() indicating the extended year corresponding to the WEEK_OF_YEAR field.
    static final int
    Field number for get and set indicating the raw offset from GMT in milliseconds.
  • Constructor Summary

    Constructors
    Modifier
    Constructor
    Description
    protected
    Constructs a Calendar with the default time zone and the default FORMAT locale.
    protected
    Calendar(TimeZone zone, ULocale locale)
    Constructs a calendar with the specified time zone and locale.
    protected
    Calendar(TimeZone zone, Locale aLocale)
    Constructs a calendar with the specified time zone and locale.
  • Method Summary

    Modifier and Type
    Method
    Description
    void
    add(int field, int amount)
    Add a signed amount to a specified field, using this calendar's rules.
    boolean
    after(Object when)
    Compares the time field records.
    boolean
    before(Object when)
    Compares the time field records.
    final void
    Clears the values of all the time fields.
    final void
    clear(int field)
    Clears the value in the given time field.
    Overrides Cloneable
    int
    Compares the times (in millis) represented by two Calendar objects.
    protected void
    Fills in any unset fields in the time field list.
    protected void
    Converts the current millisecond time value time to field values in fields[].
    protected final void
    computeGregorianFields(int julianDay)
    Compute the Gregorian calendar year, month, and day of month from the Julian day.
    protected int
    computeGregorianMonthStart(int year, int month)
    Compute the Julian day of a month of the Gregorian calendar.
    protected int
    Compute the Julian day number as specified by this calendar's fields.
    protected int
    Deprecated.
    ICU 60
    protected long
    Deprecated.
    This API is ICU internal only.
    protected void
    Converts the current field values in fields[] to the millisecond time value time.
    protected int
    computeZoneOffset(long millis, int millisInDay)
    Deprecated.
    ICU 60
    protected int
    computeZoneOffset(long millis, long millisInDay)
    Deprecated.
    This API is ICU internal only.
    boolean
    Compares this calendar to the specified object.
    int
    fieldDifference(Date when, int field)
    Returns the difference between the given time and the time this calendar object is set to.
    protected String
    fieldName(int field)
    Returns a string name for a field, for debugging and exceptions.
    protected static final int
    floorDivide(int numerator, int denominator)
    Divide two integers, returning the floor of the quotient.
    protected static final int
    floorDivide(int numerator, int denominator, int[] remainder)
    Divide two integers, returning the floor of the quotient, and the modulus remainder.
    protected static final int
    floorDivide(long numerator, int denominator, int[] remainder)
    Divide two integers, returning the floor of the quotient, and the modulus remainder.
    protected static final long
    floorDivide(long numerator, long denominator)
    Divide two long integers, returning the floor of the quotient.
    final int
    get(int field)
    Returns the value for a given time field.
    int
    getActualMaximum(int field)
    Returns the maximum value that this field could have, given the current date.
    int
    getActualMinimum(int field)
    Returns the minimum value that this field could have, given the current date.
    static Locale[]
    Returns the list of locales for which Calendars are installed.
    static ULocale[]
    Returns the list of locales for which Calendars are installed.
    static String
    getDateAtTimePattern(Calendar cal, ULocale uLocale, int dateStyle)
    Deprecated.
    This API is ICU internal only.
    getDateTimeFormat(int dateStyle, int timeStyle, ULocale loc)
    Returns a DateFormat appropriate to this calendar.
    getDateTimeFormat(int dateStyle, int timeStyle, Locale loc)
    Returns a DateFormat appropriate to this calendar.
    static String
    getDateTimePattern(Calendar cal, ULocale uLocale, int dateStyle)
    Deprecated.
    This API is ICU internal only.
    int
    getDayOfWeekType(int dayOfWeek)
    protected int
    getDefaultDayInMonth(int extendedYear, int month)
    Subclasses may override this.
    protected int
    getDefaultMonthInYear(int extendedYear)
    Subclasses may override this.
    Returns the name of this calendar in the language of the given locale.
    Returns the name of this calendar in the language of the given locale.
    final int
    Returns the number of fields defined by this calendar.
    protected int[][][]
    Returns the field resolution array for this calendar.
    int
    Returns what the first day of the week is, where 1 = SUNDAY and 7 = SATURDAY.
    final int
    getGreatestMinimum(int field)
    Returns the highest minimum value for the given field if varies.
    protected final int
    Returns the day of month (1-based) on the Gregorian calendar as computed by computeGregorianFields().
    protected final int
    Returns the day of year (1-based) on the Gregorian calendar as computed by computeGregorianFields().
    protected final int
    Returns the month (0-based) on the Gregorian calendar as computed by computeGregorianFields().
    protected final int
    Returns the extended year on the Gregorian calendar as computed by computeGregorianFields().
    static Calendar
    Returns a calendar using the default time zone and locale.
    static Calendar
    Returns a calendar using the specified time zone and default locale.
    static Calendar
    getInstance(TimeZone zone, ULocale locale)
    Returns a calendar with the specified time zone and locale.
    static Calendar
    getInstance(TimeZone zone, Locale aLocale)
    Returns a calendar with the specified time zone and locale.
    static Calendar
    Returns a calendar using the default time zone and specified locale.
    static Calendar
    Returns a calendar using the default time zone and specified locale.
    static final String[]
    getKeywordValuesForLocale(String key, ULocale locale, boolean commonlyUsed)
    Given a key and a locale, returns an array of string values in a preferred order that would make a difference.
    final int
    getLeastMaximum(int field)
    Returns the lowest maximum value for the given field if varies.
    protected int
    getLimit(int field, int limitType)
    Returns a limit for a field.
    final ULocale
    Returns the locale that was used to create this object, or null.
    final int
    getMaximum(int field)
    Returns the maximum value for the given time field.
    int
    Returns what the minimal days required in the first week of the year are.
    final int
    getMinimum(int field)
    Returns the minimum value for the given time field.
    final int
    Deprecated.
    This API is ICU internal only.
    int
    Gets the behavior for handling wall time repeating multiple times at negative time zone offset transitions.
    int
    Gets the behavior for handling skipped wall time at positive time zone offset transitions.
    protected final int
    getStamp(int field)
    Returns the timestamp of a field.
    final Date
    Returns this Calendar's current time.
    long
    Returns this Calendar's current time as a long.
    Returns the time zone.
    Returns the calendar type name string for this Calendar object.
    Return simple, immutable struct-like class for access to the week data in this calendar.
    Return simple, immutable struct-like class for access to the CLDR week data.
    int
    getWeekendTransition(int dayOfWeek)
    protected static final int
    gregorianMonthLength(int y, int m)
    Returns the length of a month of the Gregorian calendar.
    protected static final int
    Returns the length of a previous month of the Gregorian calendar.
    protected void
    handleComputeFields(int julianDay)
    Subclasses may override this method to compute several fields specific to each calendar system.
    protected int
    handleComputeJulianDay(int bestField)
    Subclasses may override this.
    protected abstract int
    handleComputeMonthStart(int eyear, int month, boolean useMonth)
    Returns the Julian day number of day before the first day of the given month in the given extended year.
    protected int[]
    Subclasses that use additional fields beyond those defined in Calendar should override this method to return an int[] array of the appropriate length.
    protected DateFormat
    Creates a DateFormat appropriate to this calendar.
    protected DateFormat
    handleGetDateFormat(String pattern, String override, ULocale locale)
    Creates a DateFormat appropriate to this calendar.
    protected DateFormat
    handleGetDateFormat(String pattern, String override, Locale locale)
    Creates a DateFormat appropriate to this calendar.
    protected DateFormat
    handleGetDateFormat(String pattern, Locale locale)
    Creates a DateFormat appropriate to this calendar.
    protected abstract int
    Returns the extended year defined by the current fields.
    protected abstract int
    handleGetLimit(int field, int limitType)
    Subclass API for defining limits of different types.
    protected int
    handleGetMonthLength(int extendedYear, int month)
    Returns the number of days in the given month of the given extended year of this calendar system.
    protected int
    Returns the number of days in the given extended year of this calendar system.
    int
    Returns a hash code for this calendar.
    boolean
    Deprecated.
    This API is ICU internal only.
    protected final int
    internalGet(int field)
    Returns the value for a given time field.
    protected final int
    internalGet(int field, int defaultValue)
    Returns the value for a given time field, or return the given default value if the field is not set.
    protected final long
    Returns the current milliseconds without recomputing.
    protected final void
    internalSet(int field, int value)
    Set a field to a value.
    boolean
    Returns true if the given Calendar object is equivalent to this one.
    protected static final boolean
    Determines if the given year is a leap year.
    boolean
    Tell whether date/time interpretation is to be lenient.
    final boolean
    isSet(int field)
    Determines if the given time field has a value set.
    boolean
    Returns true if this Calendar's current date and time is in the weekend in this calendar system.
    boolean
    Returns true if the given date and time is in the weekend in this calendar system.
    protected static final int
    Returns the day of week, from SUNDAY to SATURDAY, given a Julian day.
    protected static final long
    julianDayToMillis(int julian)
    Converts Julian day to time as milliseconds.
    protected static final int
    millisToJulianDay(long millis)
    Converts time as milliseconds to Julian day.
    protected int
    newerField(int defaultField, int alternateField)
    Returns the field that is newer, either defaultField, or alternateField.
    protected int
    newestStamp(int first, int last, int bestStampSoFar)
    Returns the newest stamp of a given range of fields.
    protected void
    pinField(int field)
    Adjust the specified field so that it is within the allowable range for the date to which this calendar is set.
    protected void
    prepareGetActual(int field, boolean isMinimum)
    Prepare this calendar for computing the actual minimum or maximum.
    protected int
    resolveFields(int[][][] precedenceTable)
    Given a precedence table, return the newest field combination in the table, or -1 if none is found.
    final void
    roll(int field, boolean up)
    Rolls (up/down) a single unit of time on the given field.
    void
    roll(int field, int amount)
    Rolls (up/down) a specified amount time on the given field.
    final void
    set(int field, int value)
    Sets the time field with the given value.
    final void
    set(int year, int month, int date)
    Sets the values for the fields year, month, and date.
    final void
    set(int year, int month, int date, int hour, int minute)
    Sets the values for the fields year, month, date, hour, and minute.
    final void
    set(int year, int month, int date, int hour, int minute, int second)
    Sets the values for the fields year, month, date, hour, minute, and second.
    void
    setFirstDayOfWeek(int value)
    Sets what the first day of the week is, where 1 = SUNDAY and 7 = SATURDAY.
    void
    setLenient(boolean lenient)
    Specify whether or not date/time interpretation is to be lenient.
    void
    Sets what the minimal days required in the first week of the year are.
    final void
    setRelatedYear(int year)
    Deprecated.
    This API is ICU internal only.
    void
    Sets the behavior for handling wall time repeating multiple times at negative time zone offset transitions.
    void
    Sets the behavior for handling skipped wall time at positive time zone offset transitions.
    final void
    setTime(Date date)
    Sets this Calendar's current time with the given Date.
    void
    setTimeInMillis(long millis)
    Sets this Calendar's current time from the given long value.
    void
    Sets the time zone with the given time zone value.
    Set data in this calendar based on the WeekData input.
    Returns a string representation of this calendar.
    protected void
    validateField(int field)
    Validate a single field of this calendar.
    protected final void
    validateField(int field, int min, int max)
    Validate a single field of this calendar given its minimum and maximum allowed value.
    protected void
    Ensure that each field is within its valid range by calling validateField(int) on each field that has been set.
    protected final int
    weekNumber(int dayOfPeriod, int dayOfWeek)
    Returns the week number of a day, within a period.
    protected int
    weekNumber(int desiredDay, int dayOfPeriod, int dayOfWeek)
    Returns the week number of a day, within a period.

    Methods inherited from class java.lang.Object

    finalize, getClass, notify, notifyAll, wait, wait, wait
  • Field Details

  • Constructor Details

    • Calendar

      protected Calendar()
      Constructs a Calendar with the default time zone and the default FORMAT locale.
      See Also:
    • Calendar

      protected Calendar(TimeZone zone, Locale aLocale)
      Constructs a calendar with the specified time zone and locale.
      Parameters:
      zone - the time zone to use
      aLocale - the locale for the week data
    • Calendar

      protected Calendar(TimeZone zone, ULocale locale)
      Constructs a calendar with the specified time zone and locale.
      Parameters:
      zone - the time zone to use
      locale - the ulocale for the week data
  • Method Details

    • getInstance

      public static Calendar getInstance()
      Returns a calendar using the default time zone and locale.
      Returns:
      a Calendar.
    • getInstance

      public static Calendar getInstance(TimeZone zone)
      Returns a calendar using the specified time zone and default locale.
      Parameters:
      zone - the time zone to use
      Returns:
      a Calendar.
    • getInstance

      public static Calendar getInstance(Locale aLocale)
      Returns a calendar using the default time zone and specified locale.
      Parameters:
      aLocale - the locale for the week data
      Returns:
      a Calendar.
    • getInstance

      public static Calendar getInstance(ULocale locale)
      Returns a calendar using the default time zone and specified locale.
      Parameters:
      locale - the ulocale for the week data
      Returns:
      a Calendar.
    • getInstance

      public static Calendar getInstance(TimeZone zone, Locale aLocale)
      Returns a calendar with the specified time zone and locale.
      Parameters:
      zone - the time zone to use
      aLocale - the locale for the week data
      Returns:
      a Calendar.
    • getInstance

      public static Calendar getInstance(TimeZone zone, ULocale locale)
      Returns a calendar with the specified time zone and locale.
      Parameters:
      zone - the time zone to use
      locale - the ulocale for the week data
      Returns:
      a Calendar.
    • getAvailableLocales

      public static Locale[] getAvailableLocales()
      Returns the list of locales for which Calendars are installed.
      Returns:
      the list of locales for which Calendars are installed.
    • getAvailableULocales

      public static ULocale[] getAvailableULocales()
      Returns the list of locales for which Calendars are installed.
      Returns:
      the list of locales for which Calendars are installed.
    • getKeywordValuesForLocale

      public static final String[] getKeywordValuesForLocale(String key, ULocale locale, boolean commonlyUsed)
      Given a key and a locale, returns an array of string values in a preferred order that would make a difference. These are all and only those values where the open (creation) of the service with the locale formed from the input locale plus input keyword and that value has different behavior than creation with the input locale alone.
      Parameters:
      key - one of the keys supported by this service. For now, only "calendar" is supported.
      locale - the locale
      commonlyUsed - if set to true it will return only commonly used values with the given locale in preferred order. Otherwise, it will return all the available values for the locale.
      Returns:
      an array of string values for the given key and the locale.
    • getTime

      public final Date getTime()
      Returns this Calendar's current time.
      Returns:
      the current time.
    • setTime

      public final void setTime(Date date)
      Sets this Calendar's current time with the given Date.

      Note: Calling setTime with Date(Long.MAX_VALUE) or Date(Long.MIN_VALUE) may yield incorrect field values from get(int).

      Parameters:
      date - the given Date.
    • getTimeInMillis

      public long getTimeInMillis()
      Returns this Calendar's current time as a long.
      Returns:
      the current time as UTC milliseconds from the epoch.
    • setTimeInMillis

      public void setTimeInMillis(long millis)
      Sets this Calendar's current time from the given long value. An IllegalIcuArgumentException is thrown when millis is outside the range permitted by a Calendar object when in strict mode. When in lenient mode the out of range values are pinned to their respective min/max.
      Parameters:
      millis - the new time in UTC milliseconds from the epoch.
    • get

      public final int get(int field)
      Returns the value for a given time field.
      Parameters:
      field - the given time field.
      Returns:
      the value for the given time field.
    • internalGet

      protected final int internalGet(int field)
      Returns the value for a given time field. This is an internal method for subclasses that does not trigger any calculations.
      Parameters:
      field - the given time field.
      Returns:
      the value for the given time field.
    • internalGet

      protected final int internalGet(int field, int defaultValue)
      Returns the value for a given time field, or return the given default value if the field is not set. This is an internal method for subclasses that does not trigger any calculations.
      Parameters:
      field - the given time field.
      defaultValue - value to return if field is not set
      Returns:
      the value for the given time field of defaultValue if the field is unset
    • set

      public final void set(int field, int value)
      Sets the time field with the given value.
      Parameters:
      field - the given time field.
      value - the value to be set for the given time field.
    • set

      public final void set(int year, int month, int date)
      Sets the values for the fields year, month, and date. Previous values of other fields are retained. If this is not desired, call clear() first.
      Parameters:
      year - the value used to set the YEAR time field.
      month - the value used to set the MONTH time field. Month value is 0-based. e.g., 0 for January.
      date - the value used to set the DATE time field.
    • set

      public final void set(int year, int month, int date, int hour, int minute)
      Sets the values for the fields year, month, date, hour, and minute. Previous values of other fields are retained. If this is not desired, call clear() first.
      Parameters:
      year - the value used to set the YEAR time field.
      month - the value used to set the MONTH time field. Month value is 0-based. e.g., 0 for January.
      date - the value used to set the DATE time field.
      hour - the value used to set the HOUR_OF_DAY time field.
      minute - the value used to set the MINUTE time field.
    • set

      public final void set(int year, int month, int date, int hour, int minute, int second)
      Sets the values for the fields year, month, date, hour, minute, and second. Previous values of other fields are retained. If this is not desired, call clear() first.
      Parameters:
      year - the value used to set the YEAR time field.
      month - the value used to set the MONTH time field. Month value is 0-based. e.g., 0 for January.
      date - the value used to set the DATE time field.
      hour - the value used to set the HOUR_OF_DAY time field.
      minute - the value used to set the MINUTE time field.
      second - the value used to set the SECOND time field.
    • getRelatedYear

      @Deprecated public final int getRelatedYear()
      Deprecated.
      This API is ICU internal only.
    • setRelatedYear

      @Deprecated public final void setRelatedYear(int year)
      Deprecated.
      This API is ICU internal only.
    • clear

      public final void clear()
      Clears the values of all the time fields.
    • clear

      public final void clear(int field)
      Clears the value in the given time field.
      Parameters:
      field - the time field to be cleared.
    • isSet

      public final boolean isSet(int field)
      Determines if the given time field has a value set.
      Returns:
      true if the given time field has a value set; false otherwise.
    • complete

      protected void complete()
      Fills in any unset fields in the time field list.
    • equals

      public boolean equals(Object obj)
      Compares this calendar to the specified object. The result is true if and only if the argument is not null and is a Calendar object that represents the same calendar as this object.
      Overrides:
      equals in class Object
      Parameters:
      obj - the object to compare with.
      Returns:
      true if the objects are the same; false otherwise.
    • isEquivalentTo

      public boolean isEquivalentTo(Calendar other)
      Returns true if the given Calendar object is equivalent to this one. An equivalent Calendar will behave exactly as this one does, but it may be set to a different time. By contrast, for the equals() method to return true, the other Calendar must be set to the same time.
      Parameters:
      other - the Calendar to be compared with this Calendar
    • hashCode

      public int hashCode()
      Returns a hash code for this calendar.
      Overrides:
      hashCode in class Object
      Returns:
      a hash code value for this object.
    • before

      public boolean before(Object when)
      Compares the time field records. Equivalent to comparing result of conversion to UTC.
      Parameters:
      when - the Calendar to be compared with this Calendar.
      Returns:
      true if the current time of this Calendar is before the time of Calendar when; false otherwise.
    • after

      public boolean after(Object when)
      Compares the time field records. Equivalent to comparing result of conversion to UTC.
      Parameters:
      when - the Calendar to be compared with this Calendar.
      Returns:
      true if the current time of this Calendar is after the time of Calendar when; false otherwise.
    • getActualMaximum

      public int getActualMaximum(int field)
      Returns the maximum value that this field could have, given the current date. For example, with the Gregorian date February 3, 1997 and the DAY_OF_MONTH field, the actual maximum is 28; for February 3, 1996 it is 29.

      The actual maximum computation ignores smaller fields and the current value of like-sized fields. For example, the actual maximum of the DAY_OF_YEAR or MONTH depends only on the year and supra-year fields. The actual maximum of the DAY_OF_MONTH depends, in addition, on the MONTH field and any other fields at that granularity (such as IS_LEAP_MONTH). The DAY_OF_WEEK_IN_MONTH field does not depend on the current DAY_OF_WEEK; it returns the maximum for any day of week in the current month. Likewise for the WEEK_OF_MONTH and WEEK_OF_YEAR fields.

      Parameters:
      field - the field whose maximum is desired
      Returns:
      the maximum of the given field for the current date of this calendar
      See Also:
    • getActualMinimum

      public int getActualMinimum(int field)
      Returns the minimum value that this field could have, given the current date. For most fields, this is the same as getMinimum and getGreatestMinimum. However, some fields, especially those related to week number, are more complicated.

      For example, assume getMinimalDaysInFirstWeek returns 4 and getFirstDayOfWeek returns SUNDAY. If the first day of the month is Sunday, Monday, Tuesday, or Wednesday there will be four or more days in the first week, so it will be week number 1, and getActualMinimum(WEEK_OF_MONTH) will return 1. However, if the first of the month is a Thursday, Friday, or Saturday, there are not four days in that week, so it is week number 0, and getActualMinimum(WEEK_OF_MONTH) will return 0.

      Parameters:
      field - the field whose actual minimum value is desired.
      Returns:
      the minimum of the given field for the current date of this calendar
      See Also:
    • prepareGetActual

      protected void prepareGetActual(int field, boolean isMinimum)
      Prepare this calendar for computing the actual minimum or maximum. This method modifies this calendar's fields; it is called on a temporary calendar.

      Rationale: The semantics of getActualXxx() is to return the maximum or minimum value that the given field can take, taking into account other relevant fields. In general these other fields are larger fields. For example, when computing the actual maximum DAY_OF_MONTH, the current value of DAY_OF_MONTH itself is ignored, as is the value of any field smaller.

      The time fields all have fixed minima and maxima, so we don't need to worry about them. This also lets us set the MILLISECONDS_IN_DAY to zero to erase any effects the time fields might have when computing date fields.

      DAY_OF_WEEK is adjusted specially for the WEEK_OF_MONTH and WEEK_OF_YEAR fields to ensure that they are computed correctly.

    • roll

      public final void roll(int field, boolean up)
      Rolls (up/down) a single unit of time on the given field. If the field is rolled past its maximum allowable value, it will "wrap" back to its minimum and continue rolling. For example, to roll the current date up by one day, you can call:

      roll(DATE, true)

      When rolling on the YEAR field, it will roll the year value in the range between 1 and the value returned by calling getMaximum(YEAR).

      When rolling on certain fields, the values of other fields may conflict and need to be changed. For example, when rolling the MONTH field for the Gregorian date 1/31/96 upward, the DAY_OF_MONTH field must be adjusted so that the result is 2/29/96 rather than the invalid 2/31/96.

      Rolling up always means rolling forward in time (unless the limit of the field is reached, in which case it may pin or wrap), so for the Gregorian calendar, starting with 100 BC and rolling the year up results in 99 BC. When eras have a definite beginning and end (as in the Chinese calendar, or as in most eras in the Japanese calendar) then rolling the year past either limit of the era will cause the year to wrap around. When eras only have a limit at one end, then attempting to roll the year past that limit will result in pinning the year at that limit. Note that for most calendars in which era 0 years move forward in time (such as Buddhist, Hebrew, or Islamic), it is possible for add or roll to result in negative years for era 0 (that is the only way to represent years before the calendar epoch in such calendars).

      Note: Calling roll(field, true) N times is not necessarily equivalent to calling roll(field, N). For example, imagine that you start with the date Gregorian date January 31, 1995. If you call roll(Calendar.MONTH, 2), the result will be March 31, 1995. But if you call roll(Calendar.MONTH, true), the result will be February 28, 1995. Calling it one more time will give March 28, 1995, which is usually not the desired result.

      Note: You should always use roll and add rather than attempting to perform arithmetic operations directly on the fields of a Calendar. It is quite possible for Calendar subclasses to have fields with non-linear behavior, for example missing months or days during non-leap years. The subclasses' add and roll methods will take this into account, while simple arithmetic manipulations may give invalid results.

      Parameters:
      field - the calendar field to roll.
      up - indicates if the value of the specified time field is to be rolled up or rolled down. Use true if rolling up, false otherwise.
      Throws:
      IllegalArgumentException - if the field is invalid or refers to a field that cannot be handled by this method.
      See Also:
    • roll

      public void roll(int field, int amount)
      Rolls (up/down) a specified amount time on the given field. For example, to roll the current date up by three days, you can call roll(Calendar.DATE, 3). If the field is rolled past its maximum allowable value, it will "wrap" back to its minimum and continue rolling. For example, calling roll(Calendar.DATE, 10) on a Gregorian calendar set to 4/25/96 will result in the date 4/5/96.

      When rolling on certain fields, the values of other fields may conflict and need to be changed. For example, when rolling the MONTH field for the Gregorian date 1/31/96 by +1, the DAY_OF_MONTH field must be adjusted so that the result is 2/29/96 rather than the invalid 2/31/96.

      Rolling by a positive value always means rolling forward in time (unless the limit of the field is reached, in which case it may pin or wrap), so for the Gregorian calendar, starting with 100 BC and rolling the year by + 1 results in 99 BC. When eras have a definite beginning and end (as in the Chinese calendar, or as in most eras in the Japanese calendar) then rolling the year past either limit of the era will cause the year to wrap around. When eras only have a limit at one end, then attempting to roll the year past that limit will result in pinning the year at that limit. Note that for most calendars in which era 0 years move forward in time (such as Buddhist, Hebrew, or Islamic), it is possible for add or roll to result in negative years for era 0 (that is the only way to represent years before the calendar epoch in such calendars).

      the ICU implementation of this method is able to roll all fields except for ERA, DST_OFFSET, and ZONE_OFFSET. Subclasses may, of course, add support for additional fields in their overrides of roll.

      Note: You should always use roll and add rather than attempting to perform arithmetic operations directly on the fields of a Calendar. It is quite possible for Calendar subclasses to have fields with non-linear behavior, for example missing months or days during non-leap years. The subclasses' add and roll methods will take this into account, while simple arithmetic manipulations may give invalid results.

      Subclassing:
      This implementation of roll assumes that the behavior of the field is continuous between its minimum and maximum, which are found by calling getActualMinimum and getActualMaximum. For most such fields, simple addition, subtraction, and modulus operations are sufficient to perform the roll. For week-related fields, the results of getFirstDayOfWeek and getMinimalDaysInFirstWeek are also necessary. Subclasses can override these two methods if their values differ from the defaults.

      Subclasses that have fields for which the assumption of continuity breaks down must override roll to handle those fields specially. For example, in the Hebrew calendar the month "Adar I" only occurs in leap years; in other years the calendar jumps from Shevat (month #4) to Adar (month #6). The HebrewCalendar.roll method takes this into account, so that rolling the month of Shevat by one gives the proper result (Adar) in a non-leap year.

      Parameters:
      field - the calendar field to roll.
      amount - the amount by which the field should be rolled.
      Throws:
      IllegalArgumentException - if the field is invalid or refers to a field that cannot be handled by this method.
      See Also:
    • add

      public void add(int field, int amount)
      Add a signed amount to a specified field, using this calendar's rules. For example, to add three days to the current date, you can call add(Calendar.DATE, 3).

      When adding to certain fields, the values of other fields may conflict and need to be changed. For example, when adding one to the MONTH field for the Gregorian date 1/31/96, the DAY_OF_MONTH field must be adjusted so that the result is 2/29/96 rather than the invalid 2/31/96.

      Adding a positive value always means moving forward in time, so for the Gregorian calendar, starting with 100 BC and adding +1 to year results in 99 BC (even though this actually reduces the numeric value of the field itself).

      The ICU implementation of this method is able to add to all fields except for ERA, DST_OFFSET, and ZONE_OFFSET. Subclasses may, of course, add support for additional fields in their overrides of add.

      Note: You should always use roll and add rather than attempting to perform arithmetic operations directly on the fields of a Calendar. It is quite possible for Calendar subclasses to have fields with non-linear behavior, for example missing months or days during non-leap years. The subclasses' add and roll methods will take this into account, while simple arithmetic manipulations may give invalid results.

      Subclassing:
      This implementation of add assumes that the behavior of the field is continuous between its minimum and maximum, which are found by calling getActualMinimum and getActualMaximum. For such fields, simple arithmetic operations are sufficient to perform the add.

      Subclasses that have fields for which this assumption of continuity breaks down must override add to handle those fields specially. For example, in the Hebrew calendar the month "Adar I" only occurs in leap years; in other years the calendar jumps from Shevat (month #4) to Adar (month #6). The HebrewCalendar.add method takes this into account, so that adding one month to a date in Shevat gives the proper result (Adar) in a non-leap year.

      Parameters:
      field - the time field.
      amount - the amount to add to the field.
      Throws:
      IllegalArgumentException - if the field is invalid or refers to a field that cannot be handled by this method.
      See Also:
    • getDisplayName

      public String getDisplayName(Locale loc)
      Returns the name of this calendar in the language of the given locale.
    • getDisplayName

      public String getDisplayName(ULocale loc)
      Returns the name of this calendar in the language of the given locale.
    • compareTo

      public int compareTo(Calendar that)
      Compares the times (in millis) represented by two Calendar objects.
      Specified by:
      compareTo in interface Comparable<Calendar>
      Parameters:
      that - the Calendar to compare to this.
      Returns:
      0 if the time represented by this Calendar is equal to the time represented by that Calendar, a value less than 0 if the time represented by this is before the time represented by that, and a value greater than 0 if the time represented by this is after the time represented by that.
      Throws:
      NullPointerException - if that Calendar is null.
      IllegalArgumentException - if the time of that Calendar can't be obtained because of invalid calendar values.
    • getDateTimeFormat

      public DateFormat getDateTimeFormat(int dateStyle, int timeStyle, Locale loc)
      Returns a DateFormat appropriate to this calendar. Subclasses wishing to specialize this behavior should override handleGetDateFormat(java.lang.String, java.util.Locale).
    • getDateTimeFormat

      public DateFormat getDateTimeFormat(int dateStyle, int timeStyle, ULocale loc)
      Returns a DateFormat appropriate to this calendar. Subclasses wishing to specialize this behavior should override handleGetDateFormat(java.lang.String, java.util.Locale).
    • handleGetDateFormat

      protected DateFormat handleGetDateFormat(String pattern, Locale locale)
      Creates a DateFormat appropriate to this calendar. This is a framework method for subclasses to override. This method is responsible for creating the calendar-specific DateFormat and DateFormatSymbols objects as needed.
      Parameters:
      pattern - the pattern, specific to the DateFormat subclass
      locale - the locale for which the symbols should be drawn
      Returns:
      a DateFormat appropriate to this calendar
    • handleGetDateFormat

      protected DateFormat handleGetDateFormat(String pattern, String override, Locale locale)
      Creates a DateFormat appropriate to this calendar. This is a framework method for subclasses to override. This method is responsible for creating the calendar-specific DateFormat and DateFormatSymbols objects as needed.
      Parameters:
      pattern - the pattern, specific to the DateFormat subclass
      override - The override string. A numbering system override string can take one of the following forms: 1). If just a numbering system name is specified, it applies to all numeric fields in the date format pattern. 2). To specify an alternate numbering system on a field by field basis, use the field letters from the pattern followed by an = sign, followed by the numbering system name. For example, to specify that just the year be formatted using Hebrew digits, use the override "y=hebr". Multiple overrides can be specified in a single string by separating them with a semi-colon. For example, the override string "m=thai;y=deva" would format using Thai digits for the month and Devanagari digits for the year.
      locale - the locale for which the symbols should be drawn
      Returns:
      a DateFormat appropriate to this calendar
    • handleGetDateFormat

      protected DateFormat handleGetDateFormat(String pattern, ULocale locale)
      Creates a DateFormat appropriate to this calendar. This is a framework method for subclasses to override. This method is responsible for creating the calendar-specific DateFormat and DateFormatSymbols objects as needed.
      Parameters:
      pattern - the pattern, specific to the DateFormat subclass
      locale - the locale for which the symbols should be drawn
      Returns:
      a DateFormat appropriate to this calendar
    • handleGetDateFormat

      protected DateFormat handleGetDateFormat(String pattern, String override, ULocale locale)
      Creates a DateFormat appropriate to this calendar. This is a framework method for subclasses to override. This method is responsible for creating the calendar-specific DateFormat and DateFormatSymbols objects as needed.
      Parameters:
      pattern - the pattern, specific to the DateFormat subclass
      locale - the locale for which the symbols should be drawn
      Returns:
      a DateFormat appropriate to this calendar
    • getDateTimePattern

      @Deprecated public static String getDateTimePattern(Calendar cal, ULocale uLocale, int dateStyle)
      Deprecated.
      This API is ICU internal only.
    • getDateAtTimePattern

      @Deprecated public static String getDateAtTimePattern(Calendar cal, ULocale uLocale, int dateStyle)
      Deprecated.
      This API is ICU internal only.
    • pinField

      protected void pinField(int field)
      Adjust the specified field so that it is within the allowable range for the date to which this calendar is set. For example, in a Gregorian calendar pinning the DAY_OF_MONTH field for a calendar set to April 31 would cause it to be set to April 30.

      Subclassing:
      This utility method is intended for use by subclasses that need to implement their own overrides of roll and add.

      Note: pinField is implemented in terms of getActualMinimum and getActualMaximum. If either of those methods uses a slow, iterative algorithm for a particular field, it would be unwise to attempt to call pinField for that field. If you really do need to do so, you should override this method to do something more efficient for that field.

      Parameters:
      field - The calendar field whose value should be pinned.
      See Also:
    • weekNumber

      protected int weekNumber(int desiredDay, int dayOfPeriod, int dayOfWeek)
      Returns the week number of a day, within a period. This may be the week number in a year or the week number in a month. Usually this will be a value >= 1, but if some initial days of the period are excluded from week 1, because getMinimalDaysInFirstWeek is > 1, then the week number will be zero for those initial days. This method requires the day number and day of week for some known date in the period in order to determine the day of week on the desired day.

      Subclassing:
      This method is intended for use by subclasses in implementing their computeTime and/or computeFields methods. It is often useful in getActualMinimum and getActualMaximum as well.

      This variant is handy for computing the week number of some other day of a period (often the first or last day of the period) when its day of the week is not known but the day number and day of week for some other day in the period (e.g. the current date) is known.

      Parameters:
      desiredDay - The DAY_OF_YEAR or DAY_OF_MONTH whose week number is desired. Should be 1 for the first day of the period.
      dayOfPeriod - The DAY_OF_YEAR or DAY_OF_MONTH for a day in the period whose DAY_OF_WEEK is specified by the dayOfWeek parameter. Should be 1 for first day of period.
      dayOfWeek - The DAY_OF_WEEK for the day corresponding to the dayOfPeriod parameter. 1-based with 1=Sunday.
      Returns:
      The week number (one-based), or zero if the day falls before the first week because getMinimalDaysInFirstWeek is more than one.
    • weekNumber

      protected final int weekNumber(int dayOfPeriod, int dayOfWeek)
      Returns the week number of a day, within a period. This may be the week number in a year, or the week number in a month. Usually this will be a value >= 1, but if some initial days of the period are excluded from week 1, because getMinimalDaysInFirstWeek is > 1, then the week number will be zero for those initial days. This method requires the day of week for the given date in order to determine the result.

      Subclassing:
      This method is intended for use by subclasses in implementing their computeTime and/or computeFields methods. It is often useful in getActualMinimum and getActualMaximum as well.

      Parameters:
      dayOfPeriod - The DAY_OF_YEAR or DAY_OF_MONTH whose week number is desired. Should be 1 for the first day of the period.
      dayOfWeek - The DAY_OF_WEEK for the day corresponding to the dayOfPeriod parameter. 1-based with 1=Sunday.
      Returns:
      The week number (one-based), or zero if the day falls before the first week because getMinimalDaysInFirstWeek is more than one.
    • fieldDifference

      public int fieldDifference(Date when, int field)
      Returns the difference between the given time and the time this calendar object is set to. If this calendar is set before the given time, the returned value will be positive. If this calendar is set after the given time, the returned value will be negative. The field parameter specifies the units of the return value. For example, if fieldDifference(when, Calendar.MONTH) returns 3, then this calendar is set to 3 months before when, and possibly some additional time less than one month.

      As a side effect of this call, this calendar is advanced toward when by the given amount. That is, calling this method has the side effect of calling add(field, n), where n is the return value.

      Usage: To use this method, call it first with the largest field of interest, then with progressively smaller fields. For example:

       int y = cal.fieldDifference(when, Calendar.YEAR);
       int m = cal.fieldDifference(when, Calendar.MONTH);
       int d = cal.fieldDifference(when, Calendar.DATE);
      computes the difference between cal and when in years, months, and days.

      Note: fieldDifference() is asymmetrical. That is, in the following code:

       cal.setTime(date1);
       int m1 = cal.fieldDifference(date2, Calendar.MONTH);
       int d1 = cal.fieldDifference(date2, Calendar.DATE);
       cal.setTime(date2);
       int m2 = cal.fieldDifference(date1, Calendar.MONTH);
       int d2 = cal.fieldDifference(date1, Calendar.DATE);
      one might expect that m1 == -m2 && d1 == -d2. However, this is not generally the case, because of irregularities in the underlying calendar system (e.g., the Gregorian calendar has a varying number of days per month).
      Parameters:
      when - the date to compare this calendar's time to
      field - the field in which to compute the result
      Returns:
      the difference, either positive or negative, between this calendar's time and when, in terms of field.
    • setTimeZone

      public void setTimeZone(TimeZone value)
      Sets the time zone with the given time zone value.
      Parameters:
      value - the given time zone.
    • getTimeZone

      public TimeZone getTimeZone()
      Returns the time zone.
      Returns:
      the time zone object associated with this calendar.
    • setLenient

      public void setLenient(boolean lenient)
      Specify whether or not date/time interpretation is to be lenient. With lenient interpretation, a date such as "February 942, 1996" will be treated as being equivalent to the 941st day after February 1, 1996. With strict interpretation, such dates will cause an exception to be thrown.
      See Also:
    • isLenient

      public boolean isLenient()
      Tell whether date/time interpretation is to be lenient.
    • setRepeatedWallTimeOption

      public void setRepeatedWallTimeOption(int option)
      Sets the behavior for handling wall time repeating multiple times at negative time zone offset transitions. For example, 1:30 AM on November 6, 2011 in US Eastern time (America/New_York) occurs twice; 1:30 AM EDT, then 1:30 AM EST one hour later. When WALLTIME_FIRST is used, the wall time 1:30AM in this example will be interpreted as 1:30 AM EDT (first occurrence). When WALLTIME_LAST is used, it will be interpreted as 1:30 AM EST (last occurrence). The default value is WALLTIME_LAST.
      Parameters:
      option - the behavior for handling repeating wall time, either WALLTIME_FIRST or WALLTIME_LAST.
      Throws:
      IllegalArgumentException - when option is neither WALLTIME_FIRST nor WALLTIME_LAST.
      See Also:
    • getRepeatedWallTimeOption

      public int getRepeatedWallTimeOption()
      Gets the behavior for handling wall time repeating multiple times at negative time zone offset transitions.
      Returns:
      the behavior for handling repeating wall time, either WALLTIME_FIRST or WALLTIME_LAST.
      See Also:
    • setSkippedWallTimeOption

      public void setSkippedWallTimeOption(int option)
      Sets the behavior for handling skipped wall time at positive time zone offset transitions. For example, 2:30 AM on March 13, 2011 in US Eastern time (America/New_York) does not exist because the wall time jump from 1:59 AM EST to 3:00 AM EDT. When WALLTIME_FIRST is used, 2:30 AM is interpreted as 30 minutes before 3:00 AM EDT, therefore, it will be resolved as 1:30 AM EST. When WALLTIME_LAST is used, 2:30 AM is interpreted as 31 minutes after 1:59 AM EST, therefore, it will be resolved as 3:30 AM EDT. When WALLTIME_NEXT_VALID is used, 2:30 AM will be resolved as next valid wall time, that is 3:00 AM EDT. The default value is WALLTIME_LAST.

      Note:This option is effective only when this calendar is lenient. When the calendar is strict, such non-existing wall time will cause an exception.

      Parameters:
      option - the behavior for handling skipped wall time at positive time zone offset transitions, one of WALLTIME_FIRST, WALLTIME_LAST and WALLTIME_NEXT_VALID.
      Throws:
      IllegalArgumentException - when option is not any of WALLTIME_FIRST, WALLTIME_LAST and WALLTIME_NEXT_VALID.
      See Also:
    • getSkippedWallTimeOption

      public int getSkippedWallTimeOption()
      Gets the behavior for handling skipped wall time at positive time zone offset transitions.
      Returns:
      the behavior for handling skipped wall time, one of WALLTIME_FIRST, WALLTIME_LAST and WALLTIME_NEXT_VALID.
      See Also:
    • setFirstDayOfWeek

      public void setFirstDayOfWeek(int value)
      Sets what the first day of the week is, where 1 = SUNDAY and 7 = SATURDAY.
      Parameters:
      value - the given first day of the week, where 1 = SUNDAY and 7 = SATURDAY.
    • getFirstDayOfWeek

      public int getFirstDayOfWeek()
      Returns what the first day of the week is, where 1 = SUNDAY and 7 = SATURDAY. e.g., Sunday in US, Monday in France
      Returns:
      the first day of the week, where 1 = SUNDAY and 7 = SATURDAY.
    • setMinimalDaysInFirstWeek

      public void setMinimalDaysInFirstWeek(int value)
      Sets what the minimal days required in the first week of the year are. For example, if the first week is defined as one that contains the first day of the first month of a year, call the method with value 1. If it must be a full week, use value 7.
      Parameters:
      value - the given minimal days required in the first week of the year.
    • getMinimalDaysInFirstWeek

      public int getMinimalDaysInFirstWeek()
      Returns what the minimal days required in the first week of the year are. That is, if the first week is defined as one that contains the first day of the first month of a year, getMinimalDaysInFirstWeek returns 1. If the minimal days required must be a full week, getMinimalDaysInFirstWeek returns 7.
      Returns:
      the minimal days required in the first week of the year.
    • handleGetLimit

      protected abstract int handleGetLimit(int field, int limitType)
      Subclass API for defining limits of different types. Subclasses must implement this method to return limits for the following fields:
      ERA
       YEAR
       MONTH
       WEEK_OF_YEAR
       WEEK_OF_MONTH
       DAY_OF_MONTH
       DAY_OF_YEAR
       DAY_OF_WEEK_IN_MONTH
       YEAR_WOY
       EXTENDED_YEAR
      Parameters:
      field - one of the above field numbers
      limitType - one of MINIMUM, GREATEST_MINIMUM, LEAST_MAXIMUM, or MAXIMUM
    • getLimit

      protected int getLimit(int field, int limitType)
      Returns a limit for a field.
      Parameters:
      field - the field, from 0..getFieldCount()-1
      limitType - the type specifier for the limit
      See Also:
    • getMinimum

      public final int getMinimum(int field)
      Returns the minimum value for the given time field. e.g., for Gregorian DAY_OF_MONTH, 1.
      Parameters:
      field - the given time field.
      Returns:
      the minimum value for the given time field.
    • getMaximum

      public final int getMaximum(int field)
      Returns the maximum value for the given time field. e.g. for Gregorian DAY_OF_MONTH, 31.
      Parameters:
      field - the given time field.
      Returns:
      the maximum value for the given time field.
    • getGreatestMinimum

      public final int getGreatestMinimum(int field)
      Returns the highest minimum value for the given field if varies. Otherwise same as getMinimum(). For Gregorian, no difference.
      Parameters:
      field - the given time field.
      Returns:
      the highest minimum value for the given time field.
    • getLeastMaximum

      public final int getLeastMaximum(int field)
      Returns the lowest maximum value for the given field if varies. Otherwise same as getMaximum(). e.g., for Gregorian DAY_OF_MONTH, 28.
      Parameters:
      field - the given time field.
      Returns:
      the lowest maximum value for the given time field.
    • getDayOfWeekType

      @Deprecated public int getDayOfWeekType(int dayOfWeek)
      Returns whether the given day of the week is a weekday, a weekend day, or a day that transitions from one to the other, for the locale and calendar system associated with this Calendar (the locale's region is often the most determinant factor). If a transition occurs at midnight, then the days before and after the transition will have the type WEEKDAY or WEEKEND. If a transition occurs at a time other than midnight, then the day of the transition will have the type WEEKEND_ONSET or WEEKEND_CEASE. In this case, the method getWeekendTransition() will return the point of transition.
      Parameters:
      dayOfWeek - either SUNDAY, MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, or SATURDAY
      Returns:
      either WEEKDAY, WEEKEND, WEEKEND_ONSET, or WEEKEND_CEASE
      Throws:
      IllegalArgumentException - if dayOfWeek is not between SUNDAY and SATURDAY, inclusive
      See Also:
    • getWeekendTransition

      @Deprecated public int getWeekendTransition(int dayOfWeek)
      Returns the time during the day at which the weekend begins or end in this calendar system. If getDayOfWeekType(dayOfWeek) == WEEKEND_ONSET return the time at which the weekend begins. If getDayOfWeekType(dayOfWeek) == WEEKEND_CEASE return the time at which the weekend ends. If getDayOfWeekType(dayOfWeek) has some other value, then throw an exception.
      Parameters:
      dayOfWeek - either SUNDAY, MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, or SATURDAY
      Returns:
      the milliseconds after midnight at which the weekend begins or ends
      Throws:
      IllegalArgumentException - if dayOfWeek is not WEEKEND_ONSET or WEEKEND_CEASE
      See Also:
    • isWeekend

      public boolean isWeekend(Date date)
      Returns true if the given date and time is in the weekend in this calendar system. Equivalent to calling setTime() followed by isWeekend(). Note: This method changes the time this calendar is set to.
      Parameters:
      date - the date and time
      Returns:
      true if the given date and time is part of the weekend
      See Also:
    • isWeekend

      public boolean isWeekend()
      Returns true if this Calendar's current date and time is in the weekend in this calendar system.
      Returns:
      true if the given date and time is part of the weekend
      See Also:
    • clone

      public Object clone()
      Overrides Cloneable
      Overrides:
      clone in class Object
    • toString

      public String toString()
      Returns a string representation of this calendar. This method is intended to be used only for debugging purposes, and the format of the returned string may vary between implementations. The returned string may be empty but may not be null.
      Overrides:
      toString in class Object
      Returns:
      a string representation of this calendar.
    • getWeekDataForRegion

      public static Calendar.WeekData getWeekDataForRegion(String region)
      Return simple, immutable struct-like class for access to the CLDR week data.
      Parameters:
      region - The input region. The results are undefined if the region code is not valid.
      Returns:
      the WeekData for the input region. It is never null.
    • getWeekData

      public Calendar.WeekData getWeekData()
      Return simple, immutable struct-like class for access to the week data in this calendar.
      Returns:
      the WeekData for this calendar.
    • setWeekData

      public Calendar setWeekData(Calendar.WeekData wdata)
      Set data in this calendar based on the WeekData input.
      Parameters:
      wdata - The week data to use
      Returns:
      this, for chaining
    • computeFields

      protected void computeFields()
      Converts the current millisecond time value time to field values in fields[]. This synchronizes the time field values with a new time that is set for the calendar. The time is not recomputed first; to recompute the time, then the fields, call the complete method.
      See Also:
    • computeGregorianFields

      protected final void computeGregorianFields(int julianDay)
      Compute the Gregorian calendar year, month, and day of month from the Julian day. These values are not stored in fields, but in member variables gregorianXxx. They are used for time zone computations and by subclasses that are Gregorian derivatives. Subclasses may call this method to perform a Gregorian calendar millis->fields computation. To perform a Gregorian calendar fields->millis computation, call computeGregorianMonthStart().
      See Also:
    • resolveFields

      protected int resolveFields(int[][][] precedenceTable)
      Given a precedence table, return the newest field combination in the table, or -1 if none is found.

      The precedence table is a 3-dimensional array of integers. It may be thought of as an array of groups. Each group is an array of lines. Each line is an array of field numbers. Within a line, if all fields are set, then the time stamp of the line is taken to be the stamp of the most recently set field. If any field of a line is unset, then the line fails to match. Within a group, the line with the newest time stamp is selected. The first field of the line is returned to indicate which line matched.

      In some cases, it may be desirable to map a line to field that whose stamp is NOT examined. For example, if the best field is DAY_OF_WEEK then the DAY_OF_WEEK_IN_MONTH algorithm may be used. In order to do this, insert the value REMAP_RESOLVE | F at the start of the line, where F is the desired return field value. This field will NOT be examined; it only determines the return value if the other fields in the line are the newest.

      If all lines of a group contain at least one unset field, then no line will match, and the group as a whole will fail to match. In that case, the next group will be processed. If all groups fail to match, then -1 is returned.

    • newestStamp

      protected int newestStamp(int first, int last, int bestStampSoFar)
      Returns the newest stamp of a given range of fields.
    • getStamp

      protected final int getStamp(int field)
      Returns the timestamp of a field.
    • newerField

      protected int newerField(int defaultField, int alternateField)
      Returns the field that is newer, either defaultField, or alternateField. If neither is newer or neither is set, return defaultField.
    • validateFields

      protected void validateFields()
      Ensure that each field is within its valid range by calling validateField(int) on each field that has been set. This method should only be called if this calendar is not lenient.
      See Also:
    • validateField

      protected void validateField(int field)
      Validate a single field of this calendar. Subclasses should override this method to validate any calendar-specific fields. Generic fields can be handled by Calendar.validateField().
      See Also:
    • validateField

      protected final void validateField(int field, int min, int max)
      Validate a single field of this calendar given its minimum and maximum allowed value. If the field is out of range, throw a descriptive IllegalArgumentException. Subclasses may use this method in their implementation of validateField(int).
    • computeTime

      protected void computeTime()
      Converts the current field values in fields[] to the millisecond time value time.
    • computeMillisInDay

      @Deprecated protected int computeMillisInDay()
      Deprecated.
      ICU 60
      Compute the milliseconds in the day from the fields. This is a value from 0 to 23:59:59.999 inclusive, unless fields are out of range, in which case it can be an arbitrary value. This value reflects local zone wall time.
    • computeMillisInDayLong

      @Deprecated protected long computeMillisInDayLong()
      Deprecated.
      This API is ICU internal only.
      Compute the milliseconds in the day from the fields. The standard value range is from 0 to 23:59:59.999 inclusive. This value reflects local zone wall time.
    • computeZoneOffset

      @Deprecated protected int computeZoneOffset(long millis, int millisInDay)
      Deprecated.
      ICU 60
      This method can assume EXTENDED_YEAR has been set.
      Parameters:
      millis - milliseconds of the date fields (local midnight millis)
      millisInDay - milliseconds of the time fields; may be out or range.
      Returns:
      total zone offset (raw + DST) for the given moment
    • computeZoneOffset

      @Deprecated protected int computeZoneOffset(long millis, long millisInDay)
      Deprecated.
      This API is ICU internal only.
      This method can assume EXTENDED_YEAR has been set.
      Parameters:
      millis - milliseconds of the date fields (local midnight millis)
      millisInDay - milliseconds of the time fields
      Returns:
      total zone offset (raw + DST) for the given moment
    • computeJulianDay

      protected int computeJulianDay()
      Compute the Julian day number as specified by this calendar's fields.
    • getFieldResolutionTable

      protected int[][][] getFieldResolutionTable()
      Returns the field resolution array for this calendar. Calendars that define additional fields or change the semantics of existing fields should override this method to adjust the field resolution semantics accordingly. Other subclasses should not override this method.
      See Also:
    • handleComputeMonthStart

      protected abstract int handleComputeMonthStart(int eyear, int month, boolean useMonth)
      Returns the Julian day number of day before the first day of the given month in the given extended year. Subclasses should override this method to implement their calendar system.
      Parameters:
      eyear - the extended year
      month - the zero-based month, or 0 if useMonth is false
      useMonth - if false, compute the day before the first day of the given year, otherwise, compute the day before the first day of the given month
      Returns:
      the Julian day number of the day before the first day of the given month and year
    • handleGetExtendedYear

      protected abstract int handleGetExtendedYear()
      Returns the extended year defined by the current fields. This will use the EXTENDED_YEAR field or the YEAR and supra-year fields (such as ERA) specific to the calendar system, depending on which set of fields is newer.
      Returns:
      the extended year
    • handleGetMonthLength

      protected int handleGetMonthLength(int extendedYear, int month)
      Returns the number of days in the given month of the given extended year of this calendar system. Subclasses should override this method if they can provide a more correct or more efficient implementation than the default implementation in Calendar.
    • handleGetYearLength

      protected int handleGetYearLength(int eyear)
      Returns the number of days in the given extended year of this calendar system. Subclasses should override this method if they can provide a more correct or more efficient implementation than the default implementation in Calendar.
    • handleCreateFields

      protected int[] handleCreateFields()
      Subclasses that use additional fields beyond those defined in Calendar should override this method to return an int[] array of the appropriate length. The length must be at least BASE_FIELD_COUNT and no more than MAX_FIELD_COUNT.
    • getDefaultMonthInYear

      protected int getDefaultMonthInYear(int extendedYear)
      Subclasses may override this. Called by handleComputeJulianDay. Returns the default month (0-based) for the year, taking year and era into account. Defaults to 0 (JANUARY) for Gregorian.
      Parameters:
      extendedYear - the extendedYear, as returned by handleGetExtendedYear
      Returns:
      the default month
      See Also:
    • getDefaultDayInMonth

      protected int getDefaultDayInMonth(int extendedYear, int month)
      Subclasses may override this. Called by handleComputeJulianDay. Returns the default day (1-based) for the month, taking currently-set year and era into account. Defaults to 1 for Gregorian.
      Parameters:
      extendedYear - the extendedYear, as returned by handleGetExtendedYear
      month - the month, as returned by getDefaultMonthInYear
      Returns:
      the default day of the month
      See Also:
    • handleComputeJulianDay

      protected int handleComputeJulianDay(int bestField)
      Subclasses may override this. This method calls handleGetMonthLength() to obtain the calendar-specific month length.
    • computeGregorianMonthStart

      protected int computeGregorianMonthStart(int year, int month)
      Compute the Julian day of a month of the Gregorian calendar. Subclasses may call this method to perform a Gregorian calendar fields->millis computation. To perform a Gregorian calendar millis->fields computation, call computeGregorianFields().
      Parameters:
      year - extended Gregorian year
      month - zero-based Gregorian month
      Returns:
      the Julian day number of the day before the first day of the given month in the given extended year
      See Also:
    • handleComputeFields

      protected void handleComputeFields(int julianDay)
      Subclasses may override this method to compute several fields specific to each calendar system. These are:
      • ERA
      • YEAR
      • MONTH
      • DAY_OF_MONTH
      • DAY_OF_YEAR
      • EXTENDED_YEAR
      Subclasses can refer to the DAY_OF_WEEK and DOW_LOCAL fields, which will be set when this method is called. Subclasses can also call the getGregorianXxx() methods to obtain Gregorian calendar equivalents for the given Julian day.

      In addition, subclasses should compute any subclass-specific fields, that is, fields from BASE_FIELD_COUNT to getFieldCount() - 1.

      The default implementation in Calendar implements a pure proleptic Gregorian calendar.

    • getGregorianYear

      protected final int getGregorianYear()
      Returns the extended year on the Gregorian calendar as computed by computeGregorianFields().
      See Also:
    • getGregorianMonth

      protected final int getGregorianMonth()
      Returns the month (0-based) on the Gregorian calendar as computed by computeGregorianFields().
      See Also:
    • getGregorianDayOfYear

      protected final int getGregorianDayOfYear()
      Returns the day of year (1-based) on the Gregorian calendar as computed by computeGregorianFields().
      See Also:
    • getGregorianDayOfMonth

      protected final int getGregorianDayOfMonth()
      Returns the day of month (1-based) on the Gregorian calendar as computed by computeGregorianFields().
      See Also:
    • getFieldCount

      public final int getFieldCount()
      Returns the number of fields defined by this calendar. Valid field arguments to set() and get() are 0..getFieldCount()-1.
    • internalSet

      protected final void internalSet(int field, int value)
      Set a field to a value. Subclasses should use this method when computing fields. It sets the time stamp in the stamp[] array to INTERNALLY_SET. If a field that may not be set by subclasses is passed in, an IllegalArgumentException is thrown. This prevents subclasses from modifying fields that are intended to be calendar-system invariant.
    • isGregorianLeapYear

      protected static final boolean isGregorianLeapYear(int year)
      Determines if the given year is a leap year. Returns true if the given year is a leap year.
      Parameters:
      year - the given year.
      Returns:
      true if the given year is a leap year; false otherwise.
    • gregorianMonthLength

      protected static final int gregorianMonthLength(int y, int m)
      Returns the length of a month of the Gregorian calendar.
      Parameters:
      y - the extended year
      m - the 0-based month number
      Returns:
      the number of days in the given month
    • gregorianPreviousMonthLength

      protected static final int gregorianPreviousMonthLength(int y, int m)
      Returns the length of a previous month of the Gregorian calendar.
      Parameters:
      y - the extended year
      m - the 0-based month number
      Returns:
      the number of days in the month previous to the given month
    • floorDivide

      protected static final long floorDivide(long numerator, long denominator)
      Divide two long integers, returning the floor of the quotient.

      Unlike the built-in division, this is mathematically well-behaved. E.g., -1/4 => 0 but floorDivide(-1,4) => -1.

      Parameters:
      numerator - the numerator
      denominator - a divisor which must be > 0
      Returns:
      the floor of the quotient.
    • floorDivide

      protected static final int floorDivide(int numerator, int denominator)
      Divide two integers, returning the floor of the quotient.

      Unlike the built-in division, this is mathematically well-behaved. E.g., -1/4 => 0 but floorDivide(-1,4) => -1.

      Parameters:
      numerator - the numerator
      denominator - a divisor which must be > 0
      Returns:
      the floor of the quotient.
    • floorDivide

      protected static final int floorDivide(int numerator, int denominator, int[] remainder)
      Divide two integers, returning the floor of the quotient, and the modulus remainder.

      Unlike the built-in division, this is mathematically well-behaved. E.g., -1/4 => 0 and -1%4 => -1, but floorDivide(-1,4) => -1 with remainder[0] => 3.

      Parameters:
      numerator - the numerator
      denominator - a divisor which must be > 0
      remainder - an array of at least one element in which the value numerator mod denominator is returned. Unlike numerator % denominator, this will always be non-negative.
      Returns:
      the floor of the quotient.
    • floorDivide

      protected static final int floorDivide(long numerator, int denominator, int[] remainder)
      Divide two integers, returning the floor of the quotient, and the modulus remainder.

      Unlike the built-in division, this is mathematically well-behaved. E.g., -1/4 => 0 and -1%4 => -1, but floorDivide(-1,4) => -1 with remainder[0] => 3.

      Parameters:
      numerator - the numerator
      denominator - a divisor which must be > 0
      remainder - an array of at least one element in which the value numerator mod denominator is returned. Unlike numerator % denominator, this will always be non-negative.
      Returns:
      the floor of the quotient.
    • fieldName

      protected String fieldName(int field)
      Returns a string name for a field, for debugging and exceptions.
    • millisToJulianDay

      protected static final int millisToJulianDay(long millis)
      Converts time as milliseconds to Julian day.
      Parameters:
      millis - the given milliseconds.
      Returns:
      the Julian day number.
    • julianDayToMillis

      protected static final long julianDayToMillis(int julian)
      Converts Julian day to time as milliseconds.
      Parameters:
      julian - the given Julian day number.
      Returns:
      time as milliseconds.
    • julianDayToDayOfWeek

      protected static final int julianDayToDayOfWeek(int julian)
      Returns the day of week, from SUNDAY to SATURDAY, given a Julian day.
    • internalGetTimeInMillis

      protected final long internalGetTimeInMillis()
      Returns the current milliseconds without recomputing.
    • getType

      public String getType()
      Returns the calendar type name string for this Calendar object. The returned string is the legacy ICU calendar attribute value, for example, "gregorian" or "japanese".

      See type="old type name" for the calendar attribute of locale IDs at http://www.unicode.org/reports/tr35/#Key_Type_Definitions

      Returns:
      legacy calendar type name string
    • haveDefaultCentury

      @Deprecated public boolean haveDefaultCentury()
      Deprecated.
      This API is ICU internal only.
      Returns if two digit representation of year in this calendar type customarily implies a default century (i.e. 03 -> 2003). The default implementation returns true. A subclass may return false if such practice is not applicable (for example, Chinese calendar and Japanese calendar).
      Returns:
      true if this calendar has a default century.
    • getLocale

      public final ULocale getLocale(ULocale.Type type)
      Returns the locale that was used to create this object, or null. This may may differ from the locale requested at the time of this object's creation. For example, if an object is created for locale en_US_CALIFORNIA, the actual data may be drawn from en (the actual locale), and en_US may be the most specific locale that exists (the valid locale).

      Note: This method will be implemented in ICU 3.0; ICU 2.8 contains a partial preview implementation. The actual locale is returned correctly, but the valid locale is not, in most cases.

      Parameters:
      type - type of information requested, either ULocale.VALID_LOCALE or ULocale.ACTUAL_LOCALE.
      Returns:
      the information specified by type, or null if this object was not constructed from locale data.
      See Also: