Class GregorianCalendar

java.lang.Object
java.util.Calendar
java.util.GregorianCalendar
All Implemented Interfaces:
Serializable,Cloneable,Comparable<Calendar>
public classGregorianCalendarextendsCalendar
GregorianCalendar is a concrete subclass ofCalendar and provides the standard calendar system used by most of the world.

GregorianCalendar is a hybrid calendar that supports both the Julian and Gregorian calendar systems with the support of a single discontinuity, which corresponds by default to the Gregorian date when the Gregorian calendar was instituted (October 15, 1582 in some countries, later in others). The cutover date may be changed by the caller by callingsetGregorianChange().

Historically, in those countries which adopted the Gregorian calendar first, October 4, 1582 (Julian) was thus followed by October 15, 1582 (Gregorian). 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 implementsproleptic 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 usingGregorianCalendar 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.

Week Of Year and Week Year

Values calculated for theWEEK_OF_YEAR field range from 1 to 53. The first week of a calendar year is the earliest seven day period starting ongetFirstDayOfWeek() that contains at leastgetMinimalDaysInFirstWeek() days from that year. It thus depends on the values ofgetMinimalDaysInFirstWeek(), getFirstDayOfWeek(), and the day of the week of January 1. Weeks between week 1 of one year and week 1 of the following year (exclusive) are numbered sequentially from 2 to 52 or 53 (except for year(s) involved in the Julian-Gregorian transition).

ThegetFirstDayOfWeek() and getMinimalDaysInFirstWeek() values are initialized using locale-dependent resources when constructing a GregorianCalendar.The week determination is compatible with the ISO 8601 standard when getFirstDayOfWeek() isMONDAY and getMinimalDaysInFirstWeek() is 4, which values are used in locales where the standard is preferred. These values can explicitly be set by callingsetFirstDayOfWeek() andsetMinimalDaysInFirstWeek().

Aweek year is in sync with aWEEK_OF_YEAR cycle. All weeks between the first and last weeks (inclusive) have the sameweek year value. Therefore, the first and last days of a week year may have different calendar year values.

For example, January 1, 1998 is a Thursday. If getFirstDayOfWeek() isMONDAY and getMinimalDaysInFirstWeek() is 4 (ISO 8601 standard compatible setting), then week 1 of 1998 starts on December 29, 1997, and ends on January 4, 1998. The week year is 1998 for the last three days of calendar year 1997. If, however,getFirstDayOfWeek() isSUNDAY, 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 and their week year is 1997.

Week Of Month

Values calculated for theWEEK_OF_MONTH field range from 0 to 6. Week 1 of a month (the days withWEEK_OF_MONTH = 1) is the earliest set of at leastgetMinimalDaysInFirstWeek() contiguous days in that month, ending on the day beforegetFirstDayOfWeek(). Unlike week 1 of a year, week 1 of a month may be shorter than 7 days, need not start ongetFirstDayOfWeek(), and will not include days of the previous month. Days of a month before week 1 have aWEEK_OF_MONTH of 0.

For example, ifgetFirstDayOfWeek() isSUNDAY andgetMinimalDaysInFirstWeek() is 4, then the first week of January 1998 is Sunday, January 4 through Saturday, January 10. These days have aWEEK_OF_MONTH of 1. Thursday, January 1 through Saturday, January 3 have aWEEK_OF_MONTH of 0. IfgetMinimalDaysInFirstWeek() is changed to 3, then January 1 through January 3 have aWEEK_OF_MONTH of 1.

Default Fields Values

Theclear method sets calendar field(s) undefined.GregorianCalendar uses the following default value for each calendar field if its value is undefined.

GregorianCalendar default field values
Field Default Value
ERAAD
YEAR1970
MONTHJANUARY
DAY_OF_MONTH1
DAY_OF_WEEKthe first day of week
WEEK_OF_MONTH0
DAY_OF_WEEK_IN_MONTH1
AM_PMAM
HOUR, HOUR_OF_DAY, MINUTE, SECOND, MILLISECOND0

Default values are not applicable for the fields not listed above.

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 Saving Time pdt.setStartRule(Calendar.APRIL, 1, Calendar.SUNDAY, 2 * 60 * 60 * 1000); pdt.setEndRule(Calendar.OCTOBER, -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

Since:
1.1
See Also:

  • Field Details

    • BC

      public static final int BC
      Value of theERA field indicating the period before the common era (before Christ), also known as BCE. The sequence of years at the transition fromBC toAD is ..., 2 BC, 1 BC, 1 AD, 2 AD,...
      See Also:

    • AD

      public static final int AD
      Value of theERA field indicating the common era (Anno Domini), also known as CE. The sequence of years at the transition fromBC toAD is ..., 2 BC, 1 BC, 1 AD, 2 AD,...
      See Also:

  • Constructor Details

    • GregorianCalendar

      public GregorianCalendar()
      Constructs a defaultGregorianCalendar using the current time in the default time zone with the defaultFORMAT locale.

    • GregorianCalendar

      public GregorianCalendar(TimeZone zone)
      Constructs aGregorianCalendar based on the current time in the given time zone with the defaultFORMAT locale.
      Parameters:
      zone - the given time zone.
      Throws:
      NullPointerException - ifzone isnull

    • GregorianCalendar

      public GregorianCalendar(Locale aLocale)
      Constructs aGregorianCalendar based on the current time in the default time zone with the given locale.
      Parameters:
      aLocale - the given locale.
      Throws:
      NullPointerException - ifaLocale isnull

    • GregorianCalendar

      public GregorianCalendar(TimeZone zone,Locale aLocale)
      Constructs aGregorianCalendar based on the current time in the given time zone with the given locale.
      Parameters:
      zone - the given time zone.
      aLocale - the given locale.
      Throws:
      NullPointerException - ifzone oraLocale isnull

    • GregorianCalendar

      public GregorianCalendar(int year, int month, int dayOfMonth)
      Constructs aGregorianCalendar with the given date set in the default time zone with the default locale.
      Parameters:
      year - the value used to set theYEAR calendar field in the calendar.
      month - the value used to set theMONTH calendar field in the calendar. Month value is 0-based. e.g., 0 for January.
      dayOfMonth - the value used to set theDAY_OF_MONTH calendar field in the calendar.

    • GregorianCalendar

      public GregorianCalendar(int year, int month, int dayOfMonth, int hourOfDay, int minute)
      Constructs aGregorianCalendar with the given date and time set for the default time zone with the default locale.
      Parameters:
      year - the value used to set theYEAR calendar field in the calendar.
      month - the value used to set theMONTH calendar field in the calendar. Month value is 0-based. e.g., 0 for January.
      dayOfMonth - the value used to set theDAY_OF_MONTH calendar field in the calendar.
      hourOfDay - the value used to set theHOUR_OF_DAY calendar field in the calendar.
      minute - the value used to set theMINUTE calendar field in the calendar.

    • GregorianCalendar

      public GregorianCalendar(int year, int month, int dayOfMonth, int hourOfDay, int minute, int second)
      Constructs a GregorianCalendar with the given date and time set for the default time zone with the default locale.
      Parameters:
      year - the value used to set theYEAR calendar field in the calendar.
      month - the value used to set theMONTH calendar field in the calendar. Month value is 0-based. e.g., 0 for January.
      dayOfMonth - the value used to set theDAY_OF_MONTH calendar field in the calendar.
      hourOfDay - the value used to set theHOUR_OF_DAY calendar field in the calendar.
      minute - the value used to set theMINUTE calendar field in the calendar.
      second - the value used to set theSECOND calendar field in the calendar.

  • Method Details

    • setGregorianChange

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

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

      Parameters:
      date - the given Gregorian cutover date.

    • 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 (Gregorian). Previous to this, dates will be in the Julian calendar.
      Returns:
      the Gregorian cutover date for thisGregorianCalendar object.

    • isLeapYear

      public boolean isLeapYear(int year)
      Determines if the given year is a leap year. Returnstrue if the given year is a leap year. To specify BC year numbers,1 - year number must be given. For example, year BC 4 is specified as -3.
      Parameters:
      year - the given year.
      Returns:
      true if the given year is a leap year;false otherwise.

    • getCalendarType

      public String getCalendarType()
      Returns"gregory" as the calendar type.
      Overrides:
      getCalendarType in class Calendar
      Returns:
      "gregory"
      Since:
      1.8
      See Also:

    • equals

      public boolean equals(Object obj)
      Compares thisGregorianCalendar to the specifiedObject. The result istrue if and only if the argument is aGregorianCalendar object that represents the same time value (millisecond offset from theEpoch) under the sameCalendar parameters and Gregorian change date as this object.
      Overrides:
      equals in class Calendar
      Parameters:
      obj - the object to compare with.
      Returns:
      true if this object is equal toobj;false otherwise.
      See Also:

    • hashCode

      public int hashCode()
      Generates the hash code for thisGregorianCalendar object.
      Overrides:
      hashCode in class Calendar
      Returns:
      a hash code value for this object.
      See Also:

    • add

      public void add(int field, int amount)
      Adds the specified (signed) amount of time to the given calendar field, based on the calendar's rules.

      Add rule 1. The value offield after the call minus the value offield before the call isamount, modulo any overflow that has occurred infield. 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 afterfield 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 thanDAY_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.

      Specified by:
      add in class Calendar
      Parameters:
      field - the calendar field.
      amount - the amount of date or time to be added to the field.
      Throws:
      IllegalArgumentException - iffield isZONE_OFFSET,DST_OFFSET, or unknown, or if any calendar fields have out-of-range values in non-lenient mode.
      See Also:

    • roll

      public void roll(int field, boolean up)
      Adds or subtracts (up/down) a single unit of time on the given time field without changing larger fields.

      Example: Consider aGregorianCalendar originally set to December 31, 1999. Callingroll(Calendar.MONTH, true) sets the calendar to January 31, 1999. TheYEAR field is unchanged because it is a larger field thanMONTH.

      Specified by:
      roll in class Calendar
      Parameters:
      field - the time field.
      up - indicates if the value of the specified calendar field is to be rolled up or rolled down. Usetrue if rolling up,false otherwise.
      Throws:
      IllegalArgumentException - iffield isZONE_OFFSET,DST_OFFSET, or unknown, or if any calendar fields have out-of-range values in non-lenient mode.
      See Also:

    • roll

      public void roll(int field, int amount)
      Adds a signed amount to the specified calendar field without changing larger fields. A negative roll amount means to subtract from field without changing larger fields. If the specified amount is 0, this method performs nothing.

      This method callsCalendar.complete() before adding the amount so that all the calendar fields are normalized. If there is any calendar field having an out-of-range value in non-lenient mode, then anIllegalArgumentException is thrown.

      Example: Consider aGregorianCalendar originally set to August 31, 1999. Callingroll(Calendar.MONTH, 8) sets the calendar to April 30,1999. Using aGregorianCalendar, theDAY_OF_MONTH field cannot be 31 in the month April.DAY_OF_MONTH is set to the closest possible value, 30. TheYEAR field maintains the value of 1999 because it is a larger field thanMONTH.

      Example: Consider aGregorianCalendar originally set to Sunday June 6, 1999. Callingroll(Calendar.WEEK_OF_MONTH, -1) sets the calendar to Tuesday June 1, 1999, whereas callingadd(Calendar.WEEK_OF_MONTH, -1) sets the calendar to Sunday May 30, 1999. This is because the roll rule imposes an additional constraint: TheMONTH must not change when theWEEK_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, theDAY_OF_WEEK, an invariant when changing theWEEK_OF_MONTH, is set to Tuesday, the closest possible value to Sunday (where Sunday is the first day of the week).

      Overrides:
      roll in class Calendar
      Parameters:
      field - the calendar field.
      amount - the signed amount to add tofield.
      Throws:
      IllegalArgumentException - iffield isZONE_OFFSET,DST_OFFSET, or unknown, or if any calendar fields have out-of-range values in non-lenient mode.
      Since:
      1.2
      See Also:

    • getMinimum

      public int getMinimum(int field)
      Returns the minimum value for the given calendar field of thisGregorianCalendar instance. The minimum value is defined as the smallest value returned by theget method for any possible time value, taking into consideration the current values of thegetFirstDayOfWeek,getMinimalDaysInFirstWeek,getGregorianChange andgetTimeZone methods.
      Specified by:
      getMinimum in class Calendar
      Parameters:
      field - the calendar field.
      Returns:
      the minimum value for the given calendar field.
      See Also:

    • getMaximum

      public int getMaximum(int field)
      Returns the maximum value for the given calendar field of thisGregorianCalendar instance. The maximum value is defined as the largest value returned by theget method for any possible time value, taking into consideration the current values of thegetFirstDayOfWeek,getMinimalDaysInFirstWeek,getGregorianChange andgetTimeZone methods.
      Specified by:
      getMaximum in class Calendar
      Parameters:
      field - the calendar field.
      Returns:
      the maximum value for the given calendar field.
      See Also:

    • getGreatestMinimum

      public int getGreatestMinimum(int field)
      Returns the highest minimum value for the given calendar field of thisGregorianCalendar instance. The highest minimum value is defined as the largest value returned bygetActualMinimum(int) for any possible time value, taking into consideration the current values of thegetFirstDayOfWeek,getMinimalDaysInFirstWeek,getGregorianChange andgetTimeZone methods.
      Specified by:
      getGreatestMinimum in class Calendar
      Parameters:
      field - the calendar field.
      Returns:
      the highest minimum value for the given calendar field.
      See Also:

    • getLeastMaximum

      public int getLeastMaximum(int field)
      Returns the lowest maximum value for the given calendar field of thisGregorianCalendar instance. The lowest maximum value is defined as the smallest value returned bygetActualMaximum(int) for any possible time value, taking into consideration the current values of thegetFirstDayOfWeek,getMinimalDaysInFirstWeek,getGregorianChange andgetTimeZone methods.
      Specified by:
      getLeastMaximum in class Calendar
      Parameters:
      field - the calendar field
      Returns:
      the lowest maximum value for the given calendar field.
      See Also:

    • getActualMinimum

      public int getActualMinimum(int field)
      Returns the minimum value that this calendar field could have, taking into consideration the given time value and the current values of thegetFirstDayOfWeek,getMinimalDaysInFirstWeek,getGregorianChange andgetTimeZone methods.

      For example, if the Gregorian change date is January 10, 1970 and the date of thisGregorianCalendar is January 20, 1970, the actual minimum value of theDAY_OF_MONTH field is 10 because the previous date of January 10, 1970 is December 27, 1996 (in the Julian calendar). Therefore, December 28, 1969 to January 9, 1970 don't exist.

      Overrides:
      getActualMinimum in class Calendar
      Parameters:
      field - the calendar field
      Returns:
      the minimum of the given field for the time value of thisGregorianCalendar
      Since:
      1.2
      See Also:

    • getActualMaximum

      public int getActualMaximum(int field)
      Returns the maximum value that this calendar field could have, taking into consideration the given time value and the current values of thegetFirstDayOfWeek,getMinimalDaysInFirstWeek,getGregorianChange andgetTimeZone methods. For example, if the date of this instance is February 1, 2004, the actual maximum value of theDAY_OF_MONTH field is 29 because 2004 is a leap year, and if the date of this instance is February 1, 2005, it's 28.

      This method calculates the maximum value ofWEEK_OF_YEAR based on theYEAR (calendar year) value, not theweek year. CallgetWeeksInWeekYear() to get the maximum value of WEEK_OF_YEAR in the week year of thisGregorianCalendar.

      Overrides:
      getActualMaximum in class Calendar
      Parameters:
      field - the calendar field
      Returns:
      the maximum of the given field for the time value of thisGregorianCalendar
      Since:
      1.2
      See Also:

    • isWeekDateSupported

      public final boolean isWeekDateSupported()
      Returnstrue indicating thisGregorianCalendar supports week dates.
      Overrides:
      isWeekDateSupported in class Calendar
      Returns:
      true (always)
      Since:
      1.7
      See Also:

    • getWeekYear

      public int getWeekYear()
      Returns theweek year represented by thisGregorianCalendar. The dates in the weeks between 1 and the maximum week number of the week year have the same week year value that may be one year before or after theYEAR (calendar year) value.

      This method callsCalendar.complete() before calculating the week year.

      Overrides:
      getWeekYear in class Calendar
      Returns:
      the week year represented by thisGregorianCalendar. If theERA value isBC, the year is represented by 0 or a negative number: BC 1 is 0, BC 2 is -1, BC 3 is -2, and so on.
      Throws:
      IllegalArgumentException - if any of the calendar fields is invalid in non-lenient mode.
      Since:
      1.7
      See Also:

    • setWeekDate

      public void setWeekDate(int weekYear, int weekOfYear, int dayOfWeek)
      Sets thisGregorianCalendar to the date given by the date specifiers -weekYear,weekOfYear, anddayOfWeek.weekOfYear follows theWEEK_OF_YEAR numbering. ThedayOfWeek value must be one of theDAY_OF_WEEK values:SUNDAY toSATURDAY.

      Note that the numeric day-of-week representation differs from the ISO 8601 standard, and that theweekOfYear numbering is compatible with the standard when getFirstDayOfWeek() isMONDAY and getMinimalDaysInFirstWeek() is 4.

      Unlike theset method, all of the calendar fields and the instant of time value are calculated upon return.

      IfweekOfYear is out of the valid week-of-year range inweekYear, theweekYear andweekOfYear values are adjusted in lenient mode, or anIllegalArgumentException is thrown in non-lenient mode.

      Overrides:
      setWeekDate in class Calendar
      Parameters:
      weekYear - the week year
      weekOfYear - the week number based onweekYear
      dayOfWeek - the day of week value: one of the constants for theDAY_OF_WEEK field:SUNDAY, ...,SATURDAY.
      Throws:
      IllegalArgumentException - if any of the given date specifiers is invalid, or if any of the calendar fields are inconsistent with the given date specifiers in non-lenient mode
      Since:
      1.7
      See Also:

    • getWeeksInWeekYear

      public int getWeeksInWeekYear()
      Returns the number of weeks in theweek year represented by thisGregorianCalendar.

      For example, if thisGregorianCalendar's date is December 31, 2008 withthe ISO 8601 compatible setting, this method will return 53 for the period: December 29, 2008 to January 3, 2010 whilegetActualMaximum(WEEK_OF_YEAR) will return 52 for the period: December 31, 2007 to December 28, 2008.

      Overrides:
      getWeeksInWeekYear in class Calendar
      Returns:
      the number of weeks in the week year.
      Since:
      1.7
      See Also:

    • computeFields

      protected void computeFields()
      Converts the time value (millisecond offset from theEpoch) to calendar field values. The time isnot recomputed first; to recompute the time, then the fields, call thecomplete method.
      Specified by:
      computeFields in class Calendar
      See Also:

    • computeTime

      protected void computeTime()
      Converts calendar field values to the time value (millisecond offset from theEpoch).
      Specified by:
      computeTime in class Calendar
      Throws:
      IllegalArgumentException - if any calendar fields are invalid.
      See Also:

    • toZonedDateTime

      public ZonedDateTime toZonedDateTime()
      Converts this object to aZonedDateTime that represents the same point on the time-line as thisGregorianCalendar.

      Since this object supports a Julian-Gregorian cutover date andZonedDateTime does not, it is possible that the resulting year, month and day will have different values. The result will represent the correct date in the ISO calendar system, which will also be the same value for Modified Julian Days.

      Returns:
      a zoned date-time representing the same point on the time-line as this gregorian calendar
      Since:
      1.8

    • from

      public static GregorianCalendar from(ZonedDateTime zdt)
      Obtains an instance ofGregorianCalendar with the default locale from aZonedDateTime object.

      SinceZonedDateTime does not support a Julian-Gregorian cutover date and uses ISO calendar system, the return GregorianCalendar is a pure Gregorian calendar and uses ISO 8601 standard for week definitions, which hasMONDAY as theFirstDayOfWeek and4 as the value of theMinimalDaysInFirstWeek.

      ZoneDateTime can store points on the time-line further in the future and further in the past thanGregorianCalendar. In this scenario, this method will throw anIllegalArgumentException exception.

      Parameters:
      zdt - the zoned date-time object to convert
      Returns:
      the gregorian calendar representing the same point on the time-line as the zoned date-time provided
      Throws:
      NullPointerException - ifzdt is null
      IllegalArgumentException - if the zoned date-time is too large to represent as aGregorianCalendar
      Since:
      1.8