Class GregorianCalendar

java.lang.Object
com.ibm.icu.util.Calendar
com.ibm.icu.util.GregorianCalendar
All Implemented Interfaces:
Serializable, Cloneable, Comparable<Calendar>
Direct Known Subclasses:
BuddhistCalendar, JapaneseCalendar, TaiwanCalendar
public class GregorianCalendar extends Calendar implements Cloneable
[icu enhancement] ICU's replacement for java.util.GregorianCalendar. Methods, fields, and other functionality specific to ICU are labeled '[icu]'.

GregorianCalendar is a concrete subclass of Calendar and provides the standard calendar used by most of the world.

The standard (Gregorian) calendar has 2 eras, BC and AD.

This implementation handles a single discontinuity, which corresponds by default to the date the Gregorian calendar was instituted (October 15, 1582 in some countries, later in others). The cutover date may be changed by the caller by calling setGregorianChange().

Historically, in those countries which adopted the Gregorian calendar first, October 4, 1582 was thus followed by October 15, 1582. This calendar models this correctly. Before the Gregorian cutover, GregorianCalendar implements the Julian calendar. The only difference between the Gregorian and the Julian calendar is the leap year rule. The Julian calendar specifies leap years every four years, whereas the Gregorian calendar omits century years which are not divisible by 400.

GregorianCalendar implements proleptic Gregorian and Julian calendars. That is, dates are computed by extrapolating the current rules indefinitely far backward and forward in time. As a result, GregorianCalendar may be used for all years to generate meaningful and consistent results. However, dates obtained using GregorianCalendar are historically accurate only from March 1, 4 AD onward, when modern Julian calendar rules were adopted. Before this date, leap year rules were applied irregularly, and before 45 BC the Julian calendar did not even exist.

Prior to the institution of the Gregorian calendar, New Year's Day was March 25. To avoid confusion, this calendar always uses January 1. A manual adjustment may be made if desired for dates that are prior to the Gregorian changeover and which fall between January 1 and March 24.

Values calculated for the WEEK_OF_YEAR field range from 1 to 53. Week 1 for a year is the earliest seven day period starting on getFirstDayOfWeek() that contains at least getMinimalDaysInFirstWeek() days from that year. It thus depends on the values of getMinimalDaysInFirstWeek(), getFirstDayOfWeek(), and the day of the week of January 1. Weeks between week 1 of one year and week 1 of the following year are numbered sequentially from 2 to 52 or 53 (as needed).

For example, January 1, 1998 was a Thursday. If getFirstDayOfWeek() is MONDAY and getMinimalDaysInFirstWeek() is 4 (these are the values reflecting ISO 8601 and many national standards), then week 1 of 1998 starts on December 29, 1997, and ends on January 4, 1998. If, however, getFirstDayOfWeek() is SUNDAY, then week 1 of 1998 starts on January 4, 1998, and ends on January 10, 1998; the first three days of 1998 then are part of week 53 of 1997.

Values calculated for the WEEK_OF_MONTH field range from 0 or 1 to 4 or 5. Week 1 of a month (the days with WEEK_OF_MONTH = 1) is the earliest set of at least getMinimalDaysInFirstWeek() contiguous days in that month, ending on the day before getFirstDayOfWeek(). Unlike week 1 of a year, week 1 of a month may be shorter than 7 days, need not start on getFirstDayOfWeek() , and will not include days of the previous month. Days of a month before week 1 have a WEEK_OF_MONTH of 0.

For example, if getFirstDayOfWeek() is SUNDAY and getMinimalDaysInFirstWeek() is 4, then the first week of January 1998 is Sunday, January 4 through Saturday, January 10. These days have a WEEK_OF_MONTH of 1. Thursday, January 1 through Saturday, January 3 have a WEEK_OF_MONTH of 0. If getMinimalDaysInFirstWeek() is changed to 3, then January 1 through January 3 have a WEEK_OF_MONTH of 1.

Example: 

// get the supported ids for GMT-08:00 (Pacific Standard Time)
String[] ids = TimeZone.getAvailableIDs(-8 * 60 * 60 * 1000);
// if no ids were returned, something is wrong. get out.
if (ids.length == 0)
    System.exit(0);

 // begin output
System.out.println("Current Time");

// create a Pacific Standard Time time zone
SimpleTimeZone pdt = new SimpleTimeZone(-8 * 60 * 60 * 1000, ids[0]);

// set up rules for daylight savings time
pdt.setStartRule(Calendar.MARCH, 2, Calendar.SUNDAY, 2 * 60 * 60 * 1000);
pdt.setEndRule(Calendar.NOVEMBER, 1, Calendar.SUNDAY, 2 * 60 * 60 * 1000);

// create a GregorianCalendar with the Pacific Daylight time zone
// and the current date and time
Calendar calendar = new GregorianCalendar(pdt);
Date trialTime = new Date();
calendar.setTime(trialTime);

// print out a bunch of interesting things
System.out.println("ERA: " + calendar.get(Calendar.ERA));
System.out.println("YEAR: " + calendar.get(Calendar.YEAR));
System.out.println("MONTH: " + calendar.get(Calendar.MONTH));
System.out.println("WEEK_OF_YEAR: " + calendar.get(Calendar.WEEK_OF_YEAR));
System.out.println("WEEK_OF_MONTH: " + calendar.get(Calendar.WEEK_OF_MONTH));
System.out.println("DATE: " + calendar.get(Calendar.DATE));
System.out.println("DAY_OF_MONTH: " + calendar.get(Calendar.DAY_OF_MONTH));
System.out.println("DAY_OF_YEAR: " + calendar.get(Calendar.DAY_OF_YEAR));
System.out.println("DAY_OF_WEEK: " + calendar.get(Calendar.DAY_OF_WEEK));
System.out.println("DAY_OF_WEEK_IN_MONTH: "
                   + calendar.get(Calendar.DAY_OF_WEEK_IN_MONTH));
System.out.println("AM_PM: " + calendar.get(Calendar.AM_PM));
System.out.println("HOUR: " + calendar.get(Calendar.HOUR));
System.out.println("HOUR_OF_DAY: " + calendar.get(Calendar.HOUR_OF_DAY));
System.out.println("MINUTE: " + calendar.get(Calendar.MINUTE));
System.out.println("SECOND: " + calendar.get(Calendar.SECOND));
System.out.println("MILLISECOND: " + calendar.get(Calendar.MILLISECOND));
System.out.println("ZONE_OFFSET: "
                   + (calendar.get(Calendar.ZONE_OFFSET)/(60*60*1000)));
System.out.println("DST_OFFSET: "
                   + (calendar.get(Calendar.DST_OFFSET)/(60*60*1000)));

System.out.println("Current Time, with hour reset to 3");
calendar.clear(Calendar.HOUR_OF_DAY); // so doesn't override
calendar.set(Calendar.HOUR, 3);
System.out.println("ERA: " + calendar.get(Calendar.ERA));
System.out.println("YEAR: " + calendar.get(Calendar.YEAR));
System.out.println("MONTH: " + calendar.get(Calendar.MONTH));
System.out.println("WEEK_OF_YEAR: " + calendar.get(Calendar.WEEK_OF_YEAR));
System.out.println("WEEK_OF_MONTH: " + calendar.get(Calendar.WEEK_OF_MONTH));
System.out.println("DATE: " + calendar.get(Calendar.DATE));
System.out.println("DAY_OF_MONTH: " + calendar.get(Calendar.DAY_OF_MONTH));
System.out.println("DAY_OF_YEAR: " + calendar.get(Calendar.DAY_OF_YEAR));
System.out.println("DAY_OF_WEEK: " + calendar.get(Calendar.DAY_OF_WEEK));
System.out.println("DAY_OF_WEEK_IN_MONTH: "
                   + calendar.get(Calendar.DAY_OF_WEEK_IN_MONTH));
System.out.println("AM_PM: " + calendar.get(Calendar.AM_PM));
System.out.println("HOUR: " + calendar.get(Calendar.HOUR));
System.out.println("HOUR_OF_DAY: " + calendar.get(Calendar.HOUR_OF_DAY));
System.out.println("MINUTE: " + calendar.get(Calendar.MINUTE));
System.out.println("SECOND: " + calendar.get(Calendar.SECOND));
System.out.println("MILLISECOND: " + calendar.get(Calendar.MILLISECOND));
System.out.println("ZONE_OFFSET: "
       + (calendar.get(Calendar.ZONE_OFFSET)/(60*60*1000))); // in hours
System.out.println("DST_OFFSET: "
       + (calendar.get(Calendar.DST_OFFSET)/(60*60*1000))); // in hours

GregorianCalendar usually should be instantiated using Calendar.getInstance(ULocale) passing in a ULocale with the tag "@calendar=gregorian".

Author:
Deborah Goldsmith, Mark Davis, Chen-Lieh Huang, Alan Liu
See Also:
Status:
Stable ICU 2.0.

  • Field Details

    • BC

      public static final int BC
      Value of the ERA field indicating the period before the common era (before Christ), also known as BCE. The sequence of years at the transition from BC to AD is ..., 2 BC, 1 BC, 1 AD, 2 AD,...
      See Also:
      Status:
      Stable ICU 2.0.

    • isGregorian

      protected transient boolean isGregorian
      Used by handleComputeJulianDay() and handleComputeMonthStart().
      Status:
      Stable ICU 2.0.

    • invertGregorian

      protected transient boolean invertGregorian
      Used by handleComputeJulianDay() and handleComputeMonthStart().
      Status:
      Stable ICU 2.0.

  • Constructor Details

    • GregorianCalendar

      public GregorianCalendar()
      Constructs a default GregorianCalendar using the current time in the default time zone with the default FORMAT locale.
      See Also:
      Status:
      Stable ICU 2.0.

    • GregorianCalendar

      public GregorianCalendar(TimeZone zone)
      Constructs a GregorianCalendar based on the current time in the given time zone with the default FORMAT locale.
      Parameters:
      zone - the given time zone.
      See Also:
      Status:
      Stable ICU 2.0.

    • GregorianCalendar

      public GregorianCalendar(Locale aLocale)
      Constructs a GregorianCalendar based on the current time in the default time zone with the given locale.
      Parameters:
      aLocale - the given locale.
      Status:
      Stable ICU 2.0.

    • GregorianCalendar

      public GregorianCalendar(ULocale locale)
      [icu] Constructs a GregorianCalendar based on the current time in the default time zone with the given locale.
      Parameters:
      locale - the given ulocale.
      Status:
      Stable ICU 3.2.

    • GregorianCalendar

      public GregorianCalendar(TimeZone zone, Locale aLocale)
      [icu] Constructs a GregorianCalendar based on the current time in the given time zone with the given locale.
      Parameters:
      zone - the given time zone.
      aLocale - the given locale.
      Status:
      Stable ICU 2.0.

    • GregorianCalendar

      public GregorianCalendar(TimeZone zone, ULocale locale)
      Constructs a GregorianCalendar based on the current time in the given time zone with the given locale.
      Parameters:
      zone - the given time zone.
      locale - the given ulocale.
      Status:
      Stable ICU 3.2.

    • GregorianCalendar

      public GregorianCalendar(int year, int month, int date)
      Constructs a GregorianCalendar with the given date set in the default time zone with the default FORMAT locale.
      Parameters:
      year - the value used to set the YEAR time field in the calendar.
      month - the value used to set the MONTH time field in the calendar. Month value is 0-based. e.g., 0 for January.
      date - the value used to set the DATE time field in the calendar.
      See Also:
      Status:
      Stable ICU 2.0.

    • GregorianCalendar

      public GregorianCalendar(int year, int month, int date, int hour, int minute)
      Constructs a GregorianCalendar with the given date and time set for the default time zone with the default FORMAT locale.
      Parameters:
      year - the value used to set the YEAR time field in the calendar.
      month - the value used to set the MONTH time field in the calendar. Month value is 0-based. e.g., 0 for January.
      date - the value used to set the DATE time field in the calendar.
      hour - the value used to set the HOUR_OF_DAY time field in the calendar.
      minute - the value used to set the MINUTE time field in the calendar.
      See Also:
      Status:
      Stable ICU 2.0.

    • GregorianCalendar

      public GregorianCalendar(int year, int month, int date, int hour, int minute, int second)
      Constructs a GregorianCalendar with the given date and time set for the default time zone with the default FORMAT locale.
      Parameters:
      year - the value used to set the YEAR time field in the calendar.
      month - the value used to set the MONTH time field in the calendar. Month value is 0-based. e.g., 0 for January.
      date - the value used to set the DATE time field in the calendar.
      hour - the value used to set the HOUR_OF_DAY time field in the calendar.
      minute - the value used to set the MINUTE time field in the calendar.
      second - the value used to set the SECOND time field in the calendar.
      See Also:
      Status:
      Stable ICU 2.0.

  • Method Details

    • handleGetLimit

      protected int handleGetLimit(int field, int limitType)
      Description copied from class: Calendar
      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
      Specified by:
      handleGetLimit in class Calendar
      Parameters:
      field - one of the above field numbers
      limitType - one of MINIMUM, GREATEST_MINIMUM, LEAST_MAXIMUM, or MAXIMUM
      Status:
      Stable ICU 2.0.

    • setGregorianChange

      public void setGregorianChange(Date date)
      Sets the GregorianCalendar change date. This is the point when the switch from Julian dates to Gregorian dates occurred. Default is October 15, 1582. Previous to this, dates will be in the Julian calendar.

      To obtain a pure Julian calendar, set the change date to Date(Long.MAX_VALUE) . To obtain a pure Gregorian calendar, set the change date to Date(Long.MIN_VALUE) .

      Parameters:
      date - the given Gregorian cutover date.
      Status:
      Stable ICU 2.0.

    • getGregorianChange

      public final Date getGregorianChange()
      Gets the Gregorian Calendar change date. This is the point when the switch from Julian dates to Gregorian dates occurred. Default is October 15, 1582. Previous to this, dates will be in the Julian calendar.
      Returns:
      the Gregorian cutover date for this calendar.
      Status:
      Stable ICU 2.0.

    • isLeapYear

      public boolean isLeapYear(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.
      Status:
      Stable ICU 2.0.

    • isEquivalentTo

      public boolean isEquivalentTo(Calendar other)
      Returns true if the given Calendar object is equivalent to this one. Calendar override.
      Overrides:
      isEquivalentTo in class Calendar
      Parameters:
      other - the Calendar to be compared with this Calendar
      Status:
      Stable ICU 2.4.

    • hashCode

      public int hashCode()
      Override hashCode. Generates the hash code for the GregorianCalendar object
      Overrides:
      hashCode in class Calendar
      Returns:
      a hash code value for this object.
      Status:
      Stable ICU 2.0.

    • roll

      public void roll(int field, int amount)
      Roll a field by a signed amount.
      Overrides:
      roll in class Calendar
      Parameters:
      field - the calendar field to roll.
      amount - the amount by which the field should be rolled.
      See Also:
      Status:
      Stable ICU 2.0.

    • getActualMinimum

      public int getActualMinimum(int field)
      Return the minimum value that this field could have, given the current date. For the Gregorian calendar, this is the same as getMinimum() and getGreatestMinimum().
      Overrides:
      getActualMinimum in class Calendar
      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:
      Status:
      Stable ICU 2.0.

    • getActualMaximum

      public int getActualMaximum(int field)
      Return the maximum value that this field could have, given the current date. For example, with the date "Feb 3, 1997" and the DAY_OF_MONTH field, the actual maximum would be 28; for "Feb 3, 1996" it s 29. Similarly for a Hebrew calendar, for some years the actual maximum for MONTH is 12, and for others 13.
      Overrides:
      getActualMaximum in class Calendar
      Parameters:
      field - the field whose maximum is desired
      Returns:
      the maximum of the given field for the current date of this calendar
      See Also:
      Status:
      Stable ICU 2.0.

    • handleGetMonthLength

      protected int handleGetMonthLength(int extendedYear, int month)
      Description copied from class: Calendar
      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.
      Overrides:
      handleGetMonthLength in class Calendar
      Status:
      Stable ICU 2.0.

    • handleGetYearLength

      protected int handleGetYearLength(int eyear)
      Description copied from class: Calendar
      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.
      Overrides:
      handleGetYearLength in class Calendar
      Status:
      Stable ICU 2.0.

    • handleComputeFields

      protected void handleComputeFields(int julianDay)
      Override Calendar to compute several fields specific to the hybrid Gregorian-Julian calendar system. These are:
      • ERA
      • YEAR
      • MONTH
      • DAY_OF_MONTH
      • DAY_OF_YEAR
      • EXTENDED_YEAR
      Overrides:
      handleComputeFields in class Calendar
      Status:
      Stable ICU 2.0.

    • handleGetExtendedYear

      protected int handleGetExtendedYear()
      Description copied from class: Calendar
      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.
      Specified by:
      handleGetExtendedYear in class Calendar
      Returns:
      the extended year
      Status:
      Stable ICU 2.0.

    • handleComputeJulianDay

      protected int handleComputeJulianDay(int bestField)
      Description copied from class: Calendar
      Subclasses may override this. This method calls handleGetMonthLength() to obtain the calendar-specific month length.
      Overrides:
      handleComputeJulianDay in class Calendar
      Status:
      Stable ICU 2.0.

    • handleComputeMonthStart

      protected int handleComputeMonthStart(int eyear, int month, boolean useMonth)
      Return JD of start of given month/year
      Specified by:
      handleComputeMonthStart in class Calendar
      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
      Status:
      Stable ICU 2.0.

    • getType

      public String getType()
      [icu] 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

      Overrides:
      getType in class Calendar
      Returns:
      legacy calendar type name string
      Status:
      Stable ICU 3.8.

    • isEra0CountingBackward

      @Deprecated protected boolean isEra0CountingBackward()
      Deprecated.
      This API is ICU internal only.
      The year in this calendar is counting from 1 backward if the era is 0.
      Overrides:
      isEra0CountingBackward in class Calendar
      Returns:
      The year in era 0 of this calendar is counting backward from 1.
      Status:
      Internal. This API is ICU internal only.

    • clone

      public GregorianCalendar clone()
      Overrides Cloneable
      Overrides:
      clone in class Calendar
      Status:
      Stable ICU 2.0.