DthingApi: java.util.GregorianCalendar Class Reference

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,

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.

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,

may be used for all years to generate meaningful and consistent results. However, dates obtained using

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

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

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

is

MONDAY

and

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,

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

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

contiguous days in that month, ending on the day before

. Unlike week 1 of a year, week 1 of a month may be shorter than 7 days, need not start on

, and will not include days of the previous month. Days of a month before week 1 have a

of 0.

For example, if

is

SUNDAY

and

is 4, then the first week of January 1998 is Sunday, January 4 through Saturday, January 10. These days have a

of 1. Thursday, January 1 through Saturday, January 3 have a

of 0. If

is changed to 3, then January 1 through January 3 have a

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.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

See also: Calendar; TimeZone

Constructor & Destructor Documentation

◆ GregorianCalendar() [1/7]

java.util.GregorianCalendar.GregorianCalendar ( )

inline

Constructs a new

initialized to the current date and time with the default

Locale

and

TimeZone

.

◆ GregorianCalendar() [2/7]

java.util.GregorianCalendar.GregorianCalendar	(	int	year,
		int	month,
		int	day
	)

inline

Constructs a new

initialized to midnight in the default

TimeZone

and

Locale

on the specified date.

Parameters

year	the year.
month	the month.
day	the day of the month.

◆ GregorianCalendar() [3/7]

java.util.GregorianCalendar.GregorianCalendar	(	int	year,
		int	month,
		int	day,
		int	hour,
		int	minute
	)

inline

Constructs a new

initialized to the specified date and time in the default

TimeZone

and

Locale

.

Parameters

year	the year.
month	the month.
day	the day of the month.
hour	the hour.
minute	the minute.

◆ GregorianCalendar() [4/7]

java.util.GregorianCalendar.GregorianCalendar	(	int	year,
		int	month,
		int	day,
		int	hour,
		int	minute,
		int	second
	)

inline

Constructs a new

initialized to the specified date and time in the default

TimeZone

and

Locale

.

Parameters

year	the year.
month	the month.
day	the day of the month.
hour	the hour.
minute	the minute.
second	the second.

◆ GregorianCalendar() [5/7]

java.util.GregorianCalendar.GregorianCalendar ( Locale locale )

inline

Constructs a new

initialized to the current date and time and using the specified

Locale

and the default

TimeZone

.

Parameters

locale

the

Locale

.

◆ GregorianCalendar() [6/7]

java.util.GregorianCalendar.GregorianCalendar ( TimeZone timezone )

inline

Constructs a new

initialized to the current date and time and using the specified

TimeZone

and the default

Locale

.

Parameters

timezone

the

TimeZone

.

◆ GregorianCalendar() [7/7]

java.util.GregorianCalendar.GregorianCalendar	(	TimeZone	timezone,
		Locale	locale
	)

inline

Constructs a new

initialized to the current date and time and using the specified

TimeZone

and

Locale

.

Parameters

timezone	the TimeZone .
locale	the Locale .

Member Function Documentation

◆ add()

void java.util.GregorianCalendar.add	(	int	field,
		int	value
	)

inline

Adds the specified amount to a

Calendar

field.

Parameters

field	the Calendar field to modify.
value	the amount to add to the field.

Exceptions

IllegalArgumentException if the specified field is DST_OFFSET or ZONE_OFFSET.

◆ clone()

Object java.util.GregorianCalendar.clone ( )

inline

Creates new instance of

with the same properties.

Returns: a shallow copy of this
GregorianCalendar
.

◆ equals()

boolean java.util.GregorianCalendar.equals ( Object object )

inline

Compares the specified

Object

to this

and returns whether they are equal. To be equal, the

Object

must be an instance of

and have the same properties.

Parameters

object

the

Object

to compare with this