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Class java.util.Calendar

java.lang.Object
   |
   +----java.util.Calendar

public class Calendar
extends Object
implements Serializable, Cloneable

Calendar is an abstract base class for converting between a Date object and a set of integer fields such as YEAR, MONTH, DAY, HOUR, and so on. (A Date object represents a specific instant in time with millisecond precision. See java.util.Date for information about the Date class.)

Subclasses of Calendar interpret a Date according to the rules of a specific calendar system. The JDK provides one concrete subclass of Calendar: GregorianCalendar. Future subclasses could represent the various types of lunar calendars in use in many parts of the world.

Like other locale-sensitive classes, Calendar provides a class method, getInstance, for getting a generally useful object of this type. Calendar's getInstance method returns a GregorianCalendar object whose time fields have been initialized with the current date and time:

 Calendar rightNow = Calendar.getInstance();

A Calendar object can produce all the time field values needed to implement the date-time formatting for a particular language and calendar style (for example, Japanese-Gregorian, Japanese-Traditional).

When computing a Date from time fields, two special circumstances may arise: there may be insufficient information to compute the Date (such as only year and month but no day in the month), or there may be inconsistent information (such as "Tuesday, July 15, 1996" -- July 15, 1996 is actually a Monday).

Insufficient information. The calendar will use default information to specify the missing fields. This may vary by calendar; for the Gregorian calendar, the default for a field is the same as that of the start of the epoch: i.e., YEAR = 1970, MONTH = JANUARY, DATE = 1, etc.

Inconsistent information. The calendar will give preference to the combinations of fields in the following order (and disregard other inconsistent information).

 month + day-of-month
 month + week-of-month + day-of-week
 month + day-of-week-of-month + day-of-week
 day-of-year
 day-of-week + week-of-year
 hour-of-day
 ampm + hour-of-ampm

Note: for some non-Gregorian calendars, different fields may be necessary for complete disambiguation. For example, a full specification of the historial Arabic astronomical calendar requires year, month, day-of-month and day-of-week in some cases.

Note: There are certain possible ambiguities in interpretation of certain singular times, which are resolved in the following ways:

24:00:00 "belongs" to the following day. That is, 23:59 on Dec 31, 1969 < 24:00 on Jan 1, 1970 < 24:01:00 on Jan 1, 1970
Although historically not precise, midnight also belongs to "am", and noon belongs to "pm", so on the same day, 12:00 am (midnight) < 12:01 am, and 12:00 pm (noon) < 12:01 pm

The date or time format strings are not part of the definition of a calendar, as those must be modifiable or overridable by the user at runtime. Use java.text.DateFormat to format dates.

Calendar provides an API for field "rolling", where fields can be incremented or decremented, but wrap around. For example, rolling the month up in the date "September 12, 1996" results in "October 12, 1996".

Calendar also provides a date arithmetic function for adding the specified (signed) amount of time to a particular time field. For example, subtracting 5 days from the date "September 12, 1996" results in "September 7, 1996".

See Also:: Date, GregorianCalendar, TimeZone, DateFormat

AM: Useful constant for hour in 12-hour clock.
AM_PM: Useful constant for date and time.
APRIL: Useful constant for month.
areFieldsSet: The flag which tells if the time fields are set for the calendar.
AUGUST: Useful constant for month.
DATE: Useful constant for date and time.
DAY_OF_MONTH: Useful constant for date and time.
DAY_OF_WEEK: Useful constant for date and time.
DAY_OF_WEEK_IN_MONTH: Useful constant for date and time.
DAY_OF_YEAR: Useful constant for date and time.
DECEMBER: Useful constant for month.
DST_OFFSET: Useful constant for date and time.
ERA: Useful constant for date and time.
FEBRUARY: Useful constant for month.
FIELD_COUNT: Useful constant for date and time.
fields: The time fields containing values into which the millis is computed.
FRIDAY: Useful constant for days of week.
HOUR: Useful constant for date and time.
HOUR_OF_DAY: Useful constant for date and time.
isSet: The flags which tell if a specified time field for the calendar is set.
isTimeSet: The flag which indicates if the current time is set for the calendar.
JANUARY: Useful constant for month.
JULY: Useful constant for month.
JUNE: Useful constant for month.
MARCH: Useful constant for month.
MAY: Useful constant for month.
MILLISECOND: Useful constant for date and time.
MINUTE: Useful constant for date and time.
MONDAY: Useful constant for days of week.
MONTH: Useful constant for date and time.
NOVEMBER: Useful constant for month.
OCTOBER: Useful constant for month.
PM: Useful constant for hour in 12-hour clock.
SATURDAY: Useful constant for days of week.
SECOND: Useful constant for date and time.
SEPTEMBER: Useful constant for month.
SUNDAY: Useful constant for days of week.
THURSDAY: Useful constant for days of week.
time: The current time set for the calendar.
TUESDAY: Useful constant for days of week.
UNDECIMBER: Useful constant for month.
WEDNESDAY: Useful constant for days of week.
WEEK_OF_MONTH: Useful constant for date and time.
WEEK_OF_YEAR: Useful constant for date and time.
YEAR: Useful constant for date and time.
ZONE_OFFSET: Useful constant for date and time.

Calendar(): Constructs a Calendar with the default time zone as returned by TimeZone.getDefault(), and the default locale.
Calendar(TimeZone, Locale): Constructs a Calendar with the given time zone and locale.

add(int, int): Date Arithmetic function.
after(Object): Compares the time field records.
before(Object): Compares the time field records.
clear(): Clears the values of all the time fields.
clear(int): Clears the value in the given time field.
clone(): Overrides Cloneable
complete(): Fills in any unset fields in the time field list.
computeFields(): Converts UTC as milliseconds to time field values.
computeTime(): Converts Calendar's time field values to UTC as milliseconds.
equals(Object): Compares the time field records.
get(int): Gets the value for a given time field.
getAvailableLocales(): Gets the set of locales for which Calendars are installed.
getFirstDayOfWeek(): Gets what the first day of the week is; e.g., Sunday in US, Monday in France.
getGreatestMinimum(int): Gets the highest minimum value for the given field if varies.
getInstance(): Gets a Calendar using the default timezone and locale.
getInstance(Locale): Gets a Calendar using the default timezone and given locale.
getInstance(TimeZone): Gets a Calendar using the given timezone and default locale.
getInstance(TimeZone, Locale): Gets a Calendar using the given timezone and given locale.
getLeastMaximum(int): Gets the lowest maximum value for the given field if varies.
getMaximum(int): Gets the maximum value for the given time field.
getMinimalDaysInFirstWeek(): Gets what the minimal days required in the first week of the year are; e.g., if the first week is defined as one that contains the first day of the first month of a year, getMinimalDaysInFirstWeek returns 1.
getMinimum(int): Gets the minimum value for the given time field.
getTime(): Gets this Calendar's current time.
getTimeInMillis(): Gets this Calendar's current time as a long.
getTimeZone(): Gets the time zone.
internalGet(int): Gets the value for a given time field.
isLenient(): Tell whether date/time interpretation is to be lenient.
isSet(int): Determines if the given time field has a value set.
roll(int, boolean): Time Field Rolling function.
set(int, int): Sets the time field with the given value.
set(int, int, int): Sets the values for the fields year, month, and date.
set(int, int, int, int, int): Sets the values for the fields year, month, date, hour, and minute.
set(int, int, int, int, int, int): Sets the values for the fields year, month, date, hour, minute, and second.
setFirstDayOfWeek(int): Sets what the first day of the week is; e.g., Sunday in US, Monday in France.
setLenient(boolean): Specify whether or not date/time interpretation is to be lenient.
setMinimalDaysInFirstWeek(int): Sets what the minimal days required in the first week of the year are; For example, if the first week is defined as one that contains the first day of the first month of a year, call the method with value 1.
setTime(Date): Sets this Calendar's current time with the given Date.
setTimeInMillis(long): Sets this Calendar's current time from the given long value.
setTimeZone(TimeZone): Sets the time zone with the given time zone value.

ERA

Properties Public Constant 
   ERA=int

Useful constant for date and time. Used in time fields. ERA is calendar specific.

YEAR

Properties Public Constant 
   YEAR=int

Useful constant for date and time. Used in time fields.

MONTH

Properties Public Constant 
   MONTH=int

Useful constant for date and time. Used in time fields.

WEEK_OF_YEAR

Properties Public Constant 
   WEEK_OF_YEAR=int

Useful constant for date and time. Used in time fields.

WEEK_OF_MONTH

Properties Public Constant 
   WEEK_OF_MONTH=int

Useful constant for date and time. Used in time fields.

DATE

Properties Public Constant 
   DATE=int

Useful constant for date and time. Used in time fields. DATE is the time field name for day-of-month.

DAY_OF_MONTH

Properties Public Constant 
   DAY_OF_MONTH=int

Useful constant for date and time. Used in time fields. This is a synonym for DATE.

DAY_OF_YEAR

Properties Public Constant 
   DAY_OF_YEAR=int

Useful constant for date and time. Used in time fields.

DAY_OF_WEEK

Properties Public Constant 
   DAY_OF_WEEK=int

Useful constant for date and time. Used in time fields.

DAY_OF_WEEK_IN_MONTH

Properties Public Constant 
   DAY_OF_WEEK_IN_MONTH=int

Useful constant for date and time. Used in time fields.

AM_PM

Properties Public Constant 
   AM_PM=int

Useful constant for date and time. Used in time fields.

HOUR

Properties Public Constant 
   HOUR=int

Useful constant for date and time. Used in time fields. HOUR is used for the 12-hour clock.

HOUR_OF_DAY

Properties Public Constant 
   HOUR_OF_DAY=int

Useful constant for date and time. Used in time fields. HOUR_OF_DAY is used for the 24-hour clock.

MINUTE

Properties Public Constant 
   MINUTE=int

Useful constant for date and time. Used in time fields.

SECOND

Properties Public Constant 
   SECOND=int

Useful constant for date and time. Used in time fields.

MILLISECOND

Properties Public Constant 
   MILLISECOND=int

Useful constant for date and time. Used in time fields.

ZONE_OFFSET

Properties Public Constant 
   ZONE_OFFSET=int

Useful constant for date and time. Used in time fields.

DST_OFFSET

Properties Public Constant 
   DST_OFFSET=int

Useful constant for date and time. Used in time fields.

FIELD_COUNT

Properties Public Constant 
   FIELD_COUNT=int

Useful constant for date and time. FIELD_COUNT is used for the time field array creation.

SUNDAY

Properties Public Constant 
   SUNDAY=int

Useful constant for days of week. Used in GregorianCalendar.

MONDAY

Properties Public Constant 
   MONDAY=int

Useful constant for days of week. Used in GregorianCalendar.

TUESDAY

Properties Public Constant 
   TUESDAY=int

Useful constant for days of week. Used in GregorianCalendar.

WEDNESDAY

Properties Public Constant 
   WEDNESDAY=int

Useful constant for days of week. Used in GregorianCalendar.

THURSDAY

Properties Public Constant 
   THURSDAY=int

Useful constant for days of week. Used in GregorianCalendar.

FRIDAY

Properties Public Constant 
   FRIDAY=int

Useful constant for days of week. Used in GregorianCalendar.

SATURDAY

Properties Public Constant 
   SATURDAY=int

Useful constant for days of week. Used in GregorianCalendar.

JANUARY

Properties Public Constant 
   JANUARY=int

Useful constant for month. Used in GregorianCalendar. Note: Calendar month is now 0-based.

FEBRUARY

Properties Public Constant 
   FEBRUARY=int

Useful constant for month. Used in GregorianCalendar.

MARCH

Properties Public Constant 
   MARCH=int

Useful constant for month. Used in GregorianCalendar.

APRIL

Properties Public Constant 
   APRIL=int

Useful constant for month. Used in GregorianCalendar.

MAY

Properties Public Constant 
   MAY=int

Useful constant for month. Used in GregorianCalendar.

JUNE

Properties Public Constant 
   JUNE=int

Useful constant for month. Used in GregorianCalendar.

JULY

Properties Public Constant 
   JULY=int

Useful constant for month. Used in GregorianCalendar.

AUGUST

Properties Public Constant 
   AUGUST=int

Useful constant for month. Used in GregorianCalendar.

SEPTEMBER

Properties Public Constant 
   SEPTEMBER=int

Useful constant for month. Used in GregorianCalendar.

OCTOBER

Properties Public Constant 
   OCTOBER=int

Useful constant for month. Used in GregorianCalendar.

NOVEMBER

Properties Public Constant 
   NOVEMBER=int

Useful constant for month. Used in GregorianCalendar.

DECEMBER

Properties Public Constant 
   DECEMBER=int

Useful constant for month. Used in GregorianCalendar.

UNDECIMBER

Properties Public Constant 
   UNDECIMBER=int

Useful constant for month. Used in GregorianCalendar. UNDECIMBER is an artifical name. This 13th month is for lunar calendars.

Properties Public Constant 
   AM=int

Useful constant for hour in 12-hour clock. Used in GregorianCalendar.

Properties Public Constant 
   PM=int

Useful constant for hour in 12-hour clock. Used in GregorianCalendar.

fields

Properties Inheritable 
   fields[]=int

The time fields containing values into which the millis is computed.

isSet

Properties Inheritable 
   isSet[]=boolean

The flags which tell if a specified time field for the calendar is set.

time

Properties Inheritable 
   time=long

The current time set for the calendar.

isTimeSet

Properties Inheritable 
   isTimeSet=boolean

The flag which indicates if the current time is set for the calendar.

areFieldsSet

Properties Inheritable 
   areFieldsSet=boolean

The flag which tells if the time fields are set for the calendar.

Calendar

    method Calendar() Inheritable

Constructs a Calendar with the default time zone as returned by TimeZone.getDefault(), and the default locale.

See Also:: getDefault

Calendar

    method Calendar(zone=TimeZone, -
                    aLocale=Locale) Inheritable

Constructs a Calendar with the given time zone and locale.

Parameters:: zone - the given time zone.

getInstance

    method getInstance() returns Calendar public  static  protect

Gets a Calendar using the default timezone and locale.

Returns:: a Calendar.

getInstance

    method getInstance(zone=TimeZone) returns Calendar public  static  protect

Gets a Calendar using the given timezone and default locale.

Parameters:: zone - the given timezone.
Returns:: a Calendar.

getInstance

    method getInstance(aLocale=Locale) returns Calendar public  static  protect

Gets a Calendar using the default timezone and given locale.

Parameters:: aLocale - the given locale.
Returns:: a Calendar.

getInstance

    method getInstance(zone=TimeZone, -
                       aLocale=Locale) returns Calendar public  static  protect

Gets a Calendar using the given timezone and given locale.

Parameters:: zone - the given timezone.; aLocale - the given locale.
Returns:: a Calendar.

getAvailableLocales

    method getAvailableLocales() returns Locale[] public  static  protect

Gets the set of locales for which Calendars are installed.

Returns:: the set of locales for which Calendars are installed.

computeTime

    method computeTime()  Inheritable abstract

Converts Calendar's time field values to UTC as milliseconds.

computeFields

    method computeFields()  Inheritable abstract

Converts UTC as milliseconds to time field values. This allows you to sync up the time field values with a new time that is set for the calendar.

getTime

    method getTime() returns Date public   final

Gets this Calendar's current time.

Returns:: the current time.

setTime

    method setTime(date=Date)  public   final

Sets this Calendar's current time with the given Date.

Parameters:: date - the given Date.

getTimeInMillis

    method getTimeInMillis() returns long Inheritable

Gets this Calendar's current time as a long.

Returns:: the current time as milliseconds from the epoch.

setTimeInMillis

    method setTimeInMillis(millis=long)  Inheritable

Sets this Calendar's current time from the given long value.

Parameters:: date - the new time in milliseconds from the epoch.

get

    method get(field=int) returns int public   final

Gets the value for a given time field.

Parameters:: field - the given time field.
Returns:: the value for the given time field.

internalGet

    method internalGet(field=int) returns int Inheritable   final

Gets the value for a given time field. This is an internal fast time field value getter for the subclasses.

Parameters:: field - the given time field.
Returns:: the value for the given time field.

set

    method set(field=int, -
               value=int)  public   final

Sets the time field with the given value.

Parameters:: field - the given time field.; value - the value to be set for the given time field.

set

    method set(year=int, -
               month=int, -
               date=int)  public   final

Sets the values for the fields year, month, and date.

Parameters:: year - the value used to set the YEAR time field.; month - the value used to set the MONTH time field. Month value is 0-based. e.g., 0 for January.; date - the value used to set the DATE time field.

set

    method set(year=int, -
               month=int, -
               date=int, -
               hour=int, -
               minute=int)  public   final

Sets the values for the fields year, month, date, hour, and minute.

Parameters:: year - the value used to set the YEAR time field.; month - the value used to set the MONTH time field. Month value is 0-based. e.g., 0 for January.; date - the value used to set the DATE time field.; hour - the value used to set the HOUR_OF_DAY time field.; minute - the value used to set the MINUTE time field.

set

    method set(year=int, -
               month=int, -
               date=int, -
               hour=int, -
               minute=int, -
               second=int)  public   final

Sets the values for the fields year, month, date, hour, minute, and second.

Parameters:: year - the value used to set the YEAR time field.; month - the value used to set the MONTH time field. Month value is 0-based. e.g., 0 for January.; date - the value used to set the DATE time field.; hour - the value used to set the HOUR_OF_DAY time field.; minute - the value used to set the MINUTE time field.; second - the value used to set the SECOND time field.

clear

    method clear()  public   final

Clears the values of all the time fields.

clear

    method clear(field=int)  public   final

Clears the value in the given time field.

Parameters:: field - the time field to be cleared.

isSet

    method isSet(field=int) returns boolean public   final

Determines if the given time field has a value set.

Returns:: true if the given time field has a value set; false otherwise.

complete

    method complete()  Inheritable

Fills in any unset fields in the time field list.

equals

    method equals(when=Object) returns boolean public abstract

Compares the time field records. Equivalent to comparing result of conversion to UTC.

Parameters:: when - the Calendar to be compared with this Calendar.
Returns:: true if the current time of this Calendar is equal to the time of Calendar when; false otherwise.
Overrides:: equals in class Object

before

    method before(when=Object) returns boolean public abstract

Compares the time field records. Equivalent to comparing result of conversion to UTC.

Parameters:: when - the Calendar to be compared with this Calendar.
Returns:: true if the current time of this Calendar is before the time of Calendar when; false otherwise.

after

    method after(when=Object) returns boolean public abstract

Compares the time field records. Equivalent to comparing result of conversion to UTC.

Parameters:: when - the Calendar to be compared with this Calendar.
Returns:: true if the current time of this Calendar is after the time of Calendar when; false otherwise.

add

    method add(field=int, -
               amount=int)  public abstract

Date Arithmetic function. Adds the specified (signed) amount of time to the given time field, based on the calendar's rules. For example, to subtract 5 days from the current time of the calendar, you can achieve it by calling:

add(Calendar.DATE, -5).

Parameters:: field - the time field.; amount - the amount of date or time to be added to the field.

roll

    method roll(field=int, -
                up=boolean)  public abstract

Time Field Rolling function. Rolls (up/down) a single unit of time on the given time field. For example, to roll the current date up by one day, you can achieve it by calling:

roll(Calendar.DATE, true). When rolling on the year or Calendar.YEAR field, it will roll the year value in the range between 1 and the value returned by calling getMaximum(Calendar.YEAR). When rolling on the month or Calendar.MONTH field, other fields like date might conflict and, need to be changed. For instance, rolling the month on the date 01/31/96 will result in 03/02/96. When rolling on the hour-in-day or Calendar.HOUR_OF_DAY field, it will roll the hour value in the range between 0 and 23, which is zero-based.

Parameters:: field - the time field.; up - indicates if the value of the specified time field is to be rolled up or rolled down. Use true if rolling up, false otherwise.

setTimeZone

    method setTimeZone(value=TimeZone)  public

Sets the time zone with the given time zone value.

Parameters:: value - the given time zone.

getTimeZone

    method getTimeZone() returns TimeZone public

Gets the time zone.

Returns:: the time zone object associated with this calendar.

setLenient

    method setLenient(lenient=boolean)  public

Specify whether or not date/time interpretation is to be lenient. With lenient interpretation, a date such as "February 942, 1996" will be treated as being equivalent to the 941st day after February 1, 1996. With strict interpretation, such dates will cause an exception to be thrown.

See Also:: setLenient

isLenient

    method isLenient() returns boolean public

Tell whether date/time interpretation is to be lenient.

setFirstDayOfWeek

    method setFirstDayOfWeek(value=int)  public

Sets what the first day of the week is; e.g., Sunday in US, Monday in France.

Parameters:: value - the given first day of the week.

getFirstDayOfWeek

    method getFirstDayOfWeek() returns int public

Gets what the first day of the week is; e.g., Sunday in US, Monday in France.

Returns:: the first day of the week.

setMinimalDaysInFirstWeek

    method setMinimalDaysInFirstWeek(value=int)  public

Sets what the minimal days required in the first week of the year are; For example, if the first week is defined as one that contains the first day of the first month of a year, call the method with value 1. If it must be a full week, use value 7.

Parameters:: value - the given minimal days required in the first week of the year.

getMinimalDaysInFirstWeek

    method getMinimalDaysInFirstWeek() returns int public

Gets what the minimal days required in the first week of the year are; e.g., if the first week is defined as one that contains the first day of the first month of a year, getMinimalDaysInFirstWeek returns 1. If the minimal days required must be a full week, getMinimalDaysInFirstWeek returns 7.

Returns:: the minimal days required in the first week of the year.

getMinimum

    method getMinimum(field=int) returns int public abstract

Gets the minimum value for the given time field. e.g., for Gregorian DAY_OF_MONTH, 1.

Parameters:: field - the given time field.
Returns:: the minimum value for the given time field.

getMaximum

    method getMaximum(field=int) returns int public abstract

Gets the maximum value for the given time field. e.g. for Gregorian DAY_OF_MONTH, 31.

Parameters:: field - the given time field.
Returns:: the maximum value for the given time field.

getGreatestMinimum

    method getGreatestMinimum(field=int) returns int public abstract

Gets the highest minimum value for the given field if varies. Otherwise same as getMinimum(). For Gregorian, no difference.

Parameters:: field - the given time field.
Returns:: the highest minimum value for the given time field.

getLeastMaximum

    method getLeastMaximum(field=int) returns int public abstract

Gets the lowest maximum value for the given field if varies. Otherwise same as getMaximum(). e.g., for Gregorian DAY_OF_MONTH, 28.

Parameters:: field - the given time field.
Returns:: the lowest maximum value for the given time field.

clone

    method clone() returns Object public

Overrides Cloneable

Overrides:: clone in class Object

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