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:
// 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
,
TimeZone
,
Serialized FormModifier and Type | Field and Description |
---|---|
static int |
AD
Value for the AD era.
|
static int |
BC
Value for the BC era.
|
ALL_STYLES, AM, AM_PM, APRIL, areFieldsSet, AUGUST, DATE, DAY_OF_MONTH, DAY_OF_WEEK, DAY_OF_WEEK_IN_MONTH, DAY_OF_YEAR, DECEMBER, DST_OFFSET, ERA, FEBRUARY, FIELD_COUNT, fields, FRIDAY, HOUR, HOUR_OF_DAY, isSet, isTimeSet, JANUARY, JULY, JUNE, LONG, MARCH, MAY, MILLISECOND, MINUTE, MONDAY, MONTH, NOVEMBER, OCTOBER, PM, SATURDAY, SECOND, SEPTEMBER, SHORT, SUNDAY, THURSDAY, time, TUESDAY, UNDECIMBER, WEDNESDAY, WEEK_OF_MONTH, WEEK_OF_YEAR, YEAR, ZONE_OFFSET
Constructor and Description |
---|
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 . |
Modifier and Type | Method and Description |
---|---|
void |
add(int field,
int value)
Adds the specified amount to a
Calendar field. |
protected void |
computeFields()
Computes the
Calendar fields from time . |
protected void |
computeTime()
Computes
time from the Calendar fields. |
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 specified 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.
|
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 the receiver.
|
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.
|
after, before, clear, clear, clone, compareTo, complete, get, getAvailableLocales, getDisplayName, getDisplayNames, getFirstDayOfWeek, getInstance, getInstance, getInstance, getInstance, getMinimalDaysInFirstWeek, getTime, getTimeInMillis, getTimeZone, internalGet, isLenient, isSet, set, set, set, set, setFirstDayOfWeek, setLenient, setMinimalDaysInFirstWeek, setTime, setTimeInMillis, setTimeZone, toString
public static final int BC
public static final int AD
public GregorianCalendar()
GregorianCalendar
initialized to the current date and
time with the default Locale
and TimeZone
.public GregorianCalendar(int year, int month, int day)
GregorianCalendar
initialized to midnight in the default
TimeZone
and Locale
on the specified date.year
- the year.month
- the month.day
- the day of the month.public GregorianCalendar(int year, int month, int day, int hour, int minute)
GregorianCalendar
initialized to the specified date and
time in the default TimeZone
and Locale
.year
- the year.month
- the month.day
- the day of the month.hour
- the hour.minute
- the minute.public GregorianCalendar(int year, int month, int day, int hour, int minute, int second)
GregorianCalendar
initialized to the specified date and
time in the default TimeZone
and Locale
.year
- the year.month
- the month.day
- the day of the month.hour
- the hour.minute
- the minute.second
- the second.public GregorianCalendar(Locale locale)
GregorianCalendar
initialized to the current date and
time and using the specified Locale
and the default TimeZone
.locale
- the Locale
.public GregorianCalendar(TimeZone timezone)
GregorianCalendar
initialized to the current date and
time and using the specified TimeZone
and the default Locale
.timezone
- the TimeZone
.public void add(int field, int value)
Calendar
field.add
in class Calendar
field
- the Calendar
field to modify.value
- the amount to add to the field.IllegalArgumentException
- if the specified field is DST_OFFSET or ZONE_OFFSET.protected void computeFields()
Calendar
Calendar
fields from time
.computeFields
in class Calendar
protected void computeTime()
Calendar
time
from the Calendar fields.computeTime
in class Calendar
public boolean equals(Object object)
object
is a GregorianCalendar with the same
properties.equals
in class Calendar
object
- the object to compare with this object.true
if the specified object is equal to this Calendar
, false
otherwise.Object.hashCode()
public int getActualMaximum(int field)
Calendar
getActualMaximum
in class Calendar
public int getActualMinimum(int field)
getMinimum()
.getActualMinimum
in class Calendar
field
- the field.public int getGreatestMinimum(int field)
getMinimum()
.getGreatestMinimum
in class Calendar
field
- the field.public final Date getGregorianChange()
Date
which represents the gregorian change date.public int getLeastMaximum(int field)
getLeastMaximum
in class Calendar
field
- the field.public int getMaximum(int field)
getMaximum
in class Calendar
field
- the field.public int getMinimum(int field)
getMinimum
in class Calendar
field
- the field.public int hashCode()
Calendar
hashCode
in class Calendar
Calendar.equals(java.lang.Object)
public boolean isLeapYear(int year)
year
is a leap year.public void roll(int field, int value)
roll
in class Calendar
field
- the field to roll.value
- the amount to add.IllegalArgumentException
- if an invalid field is specified.public void roll(int field, boolean increment)
roll
in class Calendar
field
- the field to roll.increment
- true
to increment the field, false
to
decrement.IllegalArgumentException
- if an invalid field is specified.public void setGregorianChange(Date date)