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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 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.

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

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

When computing a Date from time fields, two special circumstances may arise: there might 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:

a. 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

b. 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.

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

      public final static int ERA

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

YEAR

      public final static int YEAR

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

MONTH

      public final static int MONTH

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

WEEK_OF_YEAR

      public final static int WEEK_OF_YEAR

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

WEEK_OF_MONTH

      public final static int WEEK_OF_MONTH

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

DATE

      public final static int DATE

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

DAY_OF_MONTH

      public final static int DAY_OF_MONTH

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

DAY_OF_YEAR

      public final static int DAY_OF_YEAR

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

DAY_OF_WEEK

      public final static int DAY_OF_WEEK

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

DAY_OF_WEEK_IN_MONTH

      public final static int DAY_OF_WEEK_IN_MONTH

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

AM_PM

      public final static int AM_PM

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

HOUR

      public final static int HOUR

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

HOUR_OF_DAY

      public final static int HOUR_OF_DAY

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

MINUTE

      public final static int MINUTE

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

SECOND

      public final static int SECOND

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

MILLISECOND

      public final static int MILLISECOND

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

ZONE_OFFSET

      public final static int ZONE_OFFSET

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

DST_OFFSET

      public final static int DST_OFFSET

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

FIELD_COUNT

      public final static int FIELD_COUNT

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

SUNDAY

      public final static int SUNDAY

  Useful constant for days of week. Used in GregorianCalendar.

MONDAY

      public final static int MONDAY

  Useful constant for days of week. Used in GregorianCalendar.

TUESDAY

      public final static int TUESDAY

  Useful constant for days of week. Used in GregorianCalendar.

WEDNESDAY

      public final static int WEDNESDAY

  Useful constant for days of week. Used in GregorianCalendar.

THURSDAY

      public final static int THURSDAY

  Useful constant for days of week. Used in GregorianCalendar.

FRIDAY

      public final static int FRIDAY

  Useful constant for days of week. Used in GregorianCalendar.

SATURDAY

      public final static int SATURDAY

  Useful constant for days of week. Used in GregorianCalendar.

JANUARY

      public final static int JANUARY

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

FEBRUARY

      public final static int FEBRUARY

  Useful constant for month. Used in GregorianCalendar.

MARCH

      public final static int MARCH

  Useful constant for month. Used in GregorianCalendar.

APRIL

      public final static int APRIL

  Useful constant for month. Used in GregorianCalendar.

MAY

      public final static int MAY

  Useful constant for month. Used in GregorianCalendar.

JUNE

      public final static int JUNE

  Useful constant for month. Used in GregorianCalendar.

JULY

      public final static int JULY

  Useful constant for month. Used in GregorianCalendar.

AUGUST

      public final static int AUGUST

  Useful constant for month. Used in GregorianCalendar.

SEPTEMBER

      public final static int SEPTEMBER

  Useful constant for month. Used in GregorianCalendar.

OCTOBER

      public final static int OCTOBER

  Useful constant for month. Used in GregorianCalendar.

NOVEMBER

      public final static int NOVEMBER

  Useful constant for month. Used in GregorianCalendar.

DECEMBER

      public final static int DECEMBER

  Useful constant for month. Used in GregorianCalendar.

UNDECIMBER

      public final static int UNDECIMBER

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

AM

      public final static int AM

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

PM

      public final static int PM

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

fields

      protected int fields[]

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

isSet

      protected boolean isSet[]

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

time

      protected long time

  The current time set for the calendar.

isTimeSet

      protected boolean isTimeSet

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

areFieldsSet

      protected boolean areFieldsSet

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

##

Calendar

      protected Calendar()

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

  See Also:
    getDefault

Calendar

      protected Calendar(TimeZone zone,
                         Locale aLocale)

  Constructs a Calendar with the given time zone and locale.

  Parameters:
    zone - the given time zone.

##

getInstance

      public static synchronized Calendar getInstance()

  Gets a Calendar using the default timezone and locale.

  Returns:
    a Calendar.

getInstance

      public static synchronized Calendar getInstance(TimeZone zone)

  Gets a Calendar using the given timezone and default locale.

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

getInstance

      public static synchronized Calendar getInstance(Locale aLocale)

  Gets a Calendar using the default timezone and given locale.

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

getInstance

      public static synchronized Calendar getInstance(TimeZone zone,
                                                      Locale aLocale)

  Gets a Calendar using the given timezone and given locale.

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

getAvailableLocales

      public static synchronized Locale[] getAvailableLocales()

  Gets the set of locales for which Calendars are installed.

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

computeTime

      protected abstract void computeTime()

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

computeFields

      protected abstract void computeFields()

  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

      public final Date getTime()

  Gets this Calendar's current time.

  Returns:
    the current time.

setTime

      public final void setTime(Date date)

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

  Parameters:
    date - the given Date.

getTimeInMillis

      protected long getTimeInMillis()

  Gets this Calendar's current time as a long.

  Returns:
    the current time as milliseconds from the epoch.

setTimeInMillis

      protected void setTimeInMillis(long millis)

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

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

get

      public final int get(int field)

  Gets the value for a given time field.

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

internalGet

      protected final int internalGet(int field)

  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

      public final void set(int field,
                            int value)

  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

      public final void set(int year,
                            int month,
                            int date)

  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

      public final void set(int year,
                            int month,
                            int date,
                            int hour,
                            int minute)

  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

      public final void set(int year,
                            int month,
                            int date,
                            int hour,
                            int minute,
                            int second)

  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

      public final void clear()

  Clears the values of all the time fields.

clear

      public final void clear(int field)

  Clears the value in the given time field.

  Parameters:
    field - the time field to be cleared.

isSet

      public final boolean isSet(int field)

  Determines if the given time field has a value set.

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

complete

      protected void complete()

  Fills in any unset fields in the time field list.

equals

      public abstract boolean equals(Object when)

  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

      public abstract boolean before(Object when)

  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

      public abstract boolean after(Object when)

  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

      public abstract void add(int field,
                               int amount)

  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

      public abstract void roll(int field,
                                boolean up)

  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

      public void setTimeZone(TimeZone value)

  Sets the time zone with the given time zone value.

  Parameters:
    value - the given time zone.

getTimeZone

      public TimeZone getTimeZone()

  Gets the time zone.

  Returns:
    the time zone object associated with this calendar.

setLenient

      public void setLenient(boolean lenient)

  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

      public boolean isLenient()

  Tell whether date/time interpretation is to be lenient.

setFirstDayOfWeek

      public void setFirstDayOfWeek(int value)

  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

      public int getFirstDayOfWeek()

  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

      public void setMinimalDaysInFirstWeek(int value)

  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

      public int 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. 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

      public abstract int getMinimum(int field)

  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

      public abstract int getMaximum(int field)

  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

      public abstract int getGreatestMinimum(int field)

  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

      public abstract int getLeastMaximum(int field)

  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

      public Object clone()

  Overrides Cloneable

  Overrides:
    clone in class Object

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