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java.lang.Object
com.ibm.icu.util.Calendar
com.ibm.icu.util.GregorianCalendar
public class GregorianCalendar
extends Calendar
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:
GregorianCalendar usually should be instantiated using// 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.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
Calendar.getInstance(ULocale)
passing in a ULocale
with the tag "@calendar=gregorian"
.
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static int |
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static int |
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protected boolean |
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protected boolean |
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Fields inherited from class com.ibm.icu.util.Calendar | |
AM , AM_PM , APRIL , AUGUST , BASE_FIELD_COUNT , DATE , DAY_OF_MONTH , DAY_OF_WEEK , DAY_OF_WEEK_IN_MONTH , DAY_OF_YEAR , DECEMBER , DOW_LOCAL , DST_OFFSET , EPOCH_JULIAN_DAY , ERA , EXTENDED_YEAR , FEBRUARY , FRIDAY , GREATEST_MINIMUM , HOUR , HOUR_OF_DAY , INTERNALLY_SET , JANUARY , JAN_1_1_JULIAN_DAY , JULIAN_DAY , JULY , JUNE , LEAST_MAXIMUM , MARCH , MAXIMUM , MAX_DATE , MAX_FIELD_COUNT , MAX_JULIAN , MAX_MILLIS , MAY , MILLISECOND , MILLISECONDS_IN_DAY , MINIMUM , MINIMUM_USER_STAMP , MINUTE , MIN_DATE , MIN_JULIAN , MIN_MILLIS , MONDAY , MONTH , NOVEMBER , OCTOBER , ONE_DAY , ONE_HOUR , ONE_MINUTE , ONE_SECOND , ONE_WEEK , PM , RESOLVE_REMAP , SATURDAY , SECOND , SEPTEMBER , SUNDAY , THURSDAY , TUESDAY , UNDECIMBER , UNSET , WEDNESDAY , WEEKDAY , WEEKEND , WEEKEND_CEASE , WEEKEND_ONSET , WEEK_OF_MONTH , WEEK_OF_YEAR , YEAR , YEAR_WOY , ZONE_OFFSET |
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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,...
- Field Value:
- 1
- See Also:
Calendar.ERA
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,...
- Field Value:
- 0
- See Also:
Calendar.ERA
protected boolean invertGregorian
Used by handleComputeJulianDay() and handleComputeMonthStart().
protected boolean isGregorian
Used by handleComputeJulianDay() and handleComputeMonthStart().
public GregorianCalendar()
Constructs a default GregorianCalendar using the current time in the default time zone with the default locale.
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.
public GregorianCalendar(TimeZone zone)
Constructs a GregorianCalendar based on the current time in the given time zone with the default locale.
- Parameters:
zone
- the given time zone.
public GregorianCalendar(TimeZone zone, Locale aLocale)
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.
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.
public GregorianCalendar(ULocale locale)
Constructs a GregorianCalendar based on the current time in the default time zone with the given locale.
- Parameters:
locale
- the given ulocale.
public GregorianCalendar(int year, int month, int date)
Constructs a GregorianCalendar with the given date set in the default time zone with the default 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.
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 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.
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 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.
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 interface Calendar
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 interface Calendar
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.
public String getType()
Return the current Calendar type.
- Returns:
- type of calendar (gregorian, etc.)
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 interface Calendar
protected int handleComputeJulianDay(int bestField)
- Overrides:
- handleComputeJulianDay in interface Calendar
protected int handleComputeMonthStart(int eyear, int month, boolean useMonth)
Return JD of start of given month/year
- Overrides:
- handleComputeMonthStart in interface Calendar
protected int handleGetExtendedYear()
- Overrides:
- handleGetExtendedYear in interface Calendar
protected int handleGetLimit(int field, int limitType)
- Overrides:
- handleGetLimit in interface Calendar
protected int handleGetMonthLength(int extendedYear, int month)
- Overrides:
- handleGetMonthLength in interface Calendar
protected int handleGetYearLength(int eyear)
- Overrides:
- handleGetYearLength in interface Calendar
public int hashCode()
Override hashCode. Generates the hash code for the GregorianCalendar object
public boolean isEquivalentTo(Calendar other)
Returns true if the given Calendar object is equivalent to this one. Calendar override.
- Overrides:
- isEquivalentTo in interface Calendar
- Parameters:
other
- the Calendar to be compared with this Calendar
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.
public void roll(int field, int amount)
Roll a field by a signed amount.
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 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.