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Added in API level 1

GregorianCalendar

public class GregorianCalendar
extends Calendar

java.lang.Object
   ↳ java.util.Calendar
     ↳ java.util.GregorianCalendar


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.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:

Summary

Constants

int AD

Value for the AD era.

int BC

Value for the BC era.

Inherited constants

From class java.util.Calendar

Inherited fields

From class java.util.Calendar

Public constructors

GregorianCalendar()

Constructs a new GregorianCalendar initialized to the current date and time with the default Locale and TimeZone.

GregorianCalendar(int year, int month, int day)

Constructs a new GregorianCalendar initialized to midnight in the default TimeZone and Locale on the specified date.

GregorianCalendar(int year, int month, int day, int hour, int minute)

Constructs a new GregorianCalendar initialized to the specified date and time in the default TimeZone and Locale.

GregorianCalendar(int year, int month, int day, int hour, int minute, int second)

Constructs a new GregorianCalendar initialized to the specified date and time in the default TimeZone and Locale.

GregorianCalendar(Locale locale)

Constructs a new GregorianCalendar initialized to the current date and time and using the specified Locale and the default TimeZone.

GregorianCalendar(TimeZone timezone)

Constructs a new GregorianCalendar initialized to the current date and time and using the specified TimeZone and the default Locale.

GregorianCalendar(TimeZone timezone, Locale locale)

Constructs a new GregorianCalendar initialized to the current date and time and using the specified TimeZone and Locale.

Public methods

void add(int field, int value)

Adds the specified amount to a Calendar field.

boolean equals(Object object)

Returns true if object is a GregorianCalendar with the same properties.

int getActualMaximum(int field)

Returns the maximum value of the given field for the current date.

int getActualMinimum(int field)

Gets the minimum value of the specified field for the current date.

int getGreatestMinimum(int field)

Gets the greatest minimum value of the specified field.

final Date getGregorianChange()

Returns the gregorian change date of this calendar.

int getLeastMaximum(int field)

Gets the smallest maximum value of the specified field.

int getMaximum(int field)

Gets the greatest maximum value of the specified field.

int getMinimum(int field)

Gets the smallest minimum value of the specified field.

int hashCode()

Returns an integer hash code for this object.

boolean isLeapYear(int year)

Returns true if year is a leap year.

void roll(int field, boolean increment)

Increments or decrements the specified field and wraps the value of the field when it goes beyond the maximum or minimum value for the current date.

void roll(int field, int value)

Adds the specified amount the specified field and wraps the value of the field when it goes beyond the maximum or minimum value for the current date.

void setGregorianChange(Date date)

Sets the gregorian change date of this calendar.

Protected methods

void computeFields()

Computes the Calendar fields from time.

void computeTime()

Computes time from the Calendar fields.

Inherited methods

From class java.util.Calendar
From class java.lang.Object
From interface java.lang.Comparable

Constants

AD

Added in API level 1
int AD

Value for the AD era.

Constant Value: 1 (0x00000001)

BC

Added in API level 1
int BC

Value for the BC era.

Constant Value: 0 (0x00000000)

Public constructors

GregorianCalendar

Added in API level 1
GregorianCalendar ()

Constructs a new GregorianCalendar initialized to the current date and time with the default Locale and TimeZone.

GregorianCalendar

Added in API level 1
GregorianCalendar (int year, 
                int month, 
                int day)

Constructs a new GregorianCalendar initialized to midnight in the default TimeZone and Locale on the specified date.

Parameters
year int: the year.
month int: the month.
day int: the day of the month.

GregorianCalendar

Added in API level 1
GregorianCalendar (int year, 
                int month, 
                int day, 
                int hour, 
                int minute)

Constructs a new GregorianCalendar initialized to the specified date and time in the default TimeZone and Locale.

Parameters
year int: the year.
month int: the month.
day int: the day of the month.
hour int: the hour.
minute int: the minute.

GregorianCalendar

Added in API level 1
GregorianCalendar (int year, 
                int month, 
                int day, 
                int hour, 
                int minute, 
                int second)

Constructs a new GregorianCalendar initialized to the specified date and time in the default TimeZone and Locale.

Parameters
year int: the year.
month int: the month.
day int: the day of the month.
hour int: the hour.
minute int: the minute.
second int: the second.

GregorianCalendar

Added in API level 1
GregorianCalendar (Locale locale)

Constructs a new GregorianCalendar initialized to the current date and time and using the specified Locale and the default TimeZone.

Parameters
locale Locale: the Locale.

GregorianCalendar

Added in API level 1
GregorianCalendar (TimeZone timezone)

Constructs a new GregorianCalendar initialized to the current date and time and using the specified TimeZone and the default Locale.

Parameters
timezone TimeZone: the TimeZone.

GregorianCalendar

Added in API level 1
GregorianCalendar (TimeZone timezone, 
                Locale locale)

Constructs a new GregorianCalendar initialized to the current date and time and using the specified TimeZone and Locale.

Parameters
timezone TimeZone: the TimeZone.
locale Locale: the Locale.

Public methods

add

Added in API level 1
void add (int field, 
                int value)

Adds the specified amount to a Calendar field.

Parameters
field int: the Calendar field to modify.
value int: the amount to add to the field.
Throws
IllegalArgumentException if the specified field is DST_OFFSET or ZONE_OFFSET.

equals

Added in API level 1
boolean equals (Object object)

Returns true if object is a GregorianCalendar with the same properties.

Parameters
object Object: the object to compare this instance with.
Returns
boolean true if the given object is equal to this Calendar, false otherwise.

getActualMaximum

Added in API level 1
int getActualMaximum (int field)

Returns the maximum value of the given field for the current date. For example, the maximum number of days in the current month.

Parameters
field int
Returns
int

getActualMinimum

Added in API level 1
int getActualMinimum (int field)

Gets the minimum value of the specified field for the current date. For the gregorian calendar, this value is the same as getMinimum().

Parameters
field int: the field.
Returns
int the minimum value of the specified field.

getGreatestMinimum

Added in API level 1
int getGreatestMinimum (int field)

Gets the greatest minimum value of the specified field. For the gregorian calendar, this value is the same as getMinimum().

Parameters
field int: the field.
Returns
int the greatest minimum value of the specified field.

getGregorianChange

Added in API level 1
Date getGregorianChange ()

Returns the gregorian change date of this calendar. This is the date on which the gregorian calendar came into effect.

Returns
Date a Date which represents the gregorian change date.

getLeastMaximum

Added in API level 1
int getLeastMaximum (int field)

Gets the smallest maximum value of the specified field. For example, 28 for the day of month field.

Parameters
field int: the field.
Returns
int the smallest maximum value of the specified field.

getMaximum

Added in API level 1
int getMaximum (int field)

Gets the greatest maximum value of the specified field. For example, 31 for the day of month field.

Parameters
field int: the field.
Returns
int the greatest maximum value of the specified field.

getMinimum

Added in API level 1
int getMinimum (int field)

Gets the smallest minimum value of the specified field.

Parameters
field int: the field.
Returns
int the smallest minimum value of the specified field.

hashCode

Added in API level 1
int hashCode ()

Returns an integer hash code for this object. By contract, any two objects for which equals(Object) returns true must return the same hash code value. This means that subclasses of Object usually override both methods or neither method.

Note that hash values must not change over time unless information used in equals comparisons also changes.

See Writing a correct hashCode method if you intend implementing your own hashCode method.

Returns
int this object's hash code.

isLeapYear

Added in API level 1
boolean isLeapYear (int year)

Returns true if year is a leap year.

Parameters
year int
Returns
boolean

roll

Added in API level 1
void roll (int field, 
                boolean increment)

Increments or decrements the specified field and wraps the value of the field when it goes beyond the maximum or minimum value for the current date. Other fields will be adjusted as required to maintain a consistent date. For example, March 31 will roll to April 30 when rolling the month field.

Parameters
field int: the field to roll.
increment boolean: true to increment the field, false to decrement.
Throws
IllegalArgumentException if an invalid field is specified.

roll

Added in API level 1
void roll (int field, 
                int value)

Adds the specified amount the specified field and wraps the value of the field when it goes beyond the maximum or minimum value for the current date. Other fields will be adjusted as required to maintain a consistent date.

Parameters
field int: the field to roll.
value int: the amount to add.
Throws
IllegalArgumentException if an invalid field is specified.

setGregorianChange

Added in API level 1
void setGregorianChange (Date date)

Sets the gregorian change date of this calendar.

Parameters
date Date

Protected methods

computeFields

Added in API level 1
void computeFields ()

Computes the Calendar fields from time.

computeTime

Added in API level 1
void computeTime ()

Computes time from the Calendar fields.

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