Class TimeZone
- All Implemented Interfaces:
Serializable
,Cloneable
- Direct Known Subclasses:
SimpleTimeZone
TimeZone
represents a time zone offset, and also figures out daylight
savings.
Typically, you get a TimeZone
using getDefault
which creates a TimeZone
based on the time zone where the program
is running. For example, for a program running in Japan, getDefault
creates a TimeZone
object based on Japanese Standard Time.
You can also get a TimeZone
using getTimeZone
along with a time zone ID. For instance, the time zone ID for the
U.S. Pacific Time zone is "America/Los_Angeles". So, you can get a
U.S. Pacific Time TimeZone
object with:
You can use theTimeZone tz = TimeZone.getTimeZone("America/Los_Angeles");
getAvailableIDs
method to iterate through
all the supported time zone IDs. You can then choose a
supported ID to get a TimeZone
.
If the time zone you want is not represented by one of the
supported IDs, then a custom time zone ID can be specified to
produce a TimeZone. The syntax of a custom time zone ID is:
Hours must be between 0 to 23 and Minutes/Seconds must be between 00 to 59. For example, "GMT+10" and "GMT+0010" mean ten hours and ten minutes ahead of GMT, respectively.CustomID:GMT
Sign Hours:
Minutes:
SecondsGMT
Sign Hours:
MinutesGMT
Sign Hours MinutesGMT
Sign Hours Sign: one of+ -
Hours: Digit Digit Digit Minutes: Digit Digit Seconds: Digit Digit Digit: one of0 1 2 3 4 5 6 7 8 9
The format is locale independent and digits must be taken from the
Basic Latin block of the Unicode standard. No daylight saving time
transition schedule can be specified with a custom time zone ID. If
the specified string doesn't match the syntax, "GMT"
is used.
When creating a TimeZone
, the specified custom time
zone ID is normalized in the following syntax:
For example, TimeZone.getTimeZone("GMT-8").getID() returns "GMT-08:00". ColonSeconds part only appears if the seconds value is non-zero.NormalizedCustomID:GMT
Sign TwoDigitHours:
Minutes [ColonSeconds] Sign: one of+ -
TwoDigitHours: Digit Digit Minutes: Digit Digit ColonSeconds::
Digit Digit Digit: one of0 1 2 3 4 5 6 7 8 9
Three-letter time zone IDs
For compatibility with JDK 1.1.x, some other three-letter time zone IDs (such as "PST", "CTT", "AST") are also supported. However, their use is deprecated because the same abbreviation is often used for multiple time zones (for example, "CST" could be U.S. "Central Standard Time" and "China Standard Time"), and the Java platform can then only recognize one of them. The full list of deprecated three-letter time zone IDs and their mappings can be viewed atZoneId.SHORT_IDS
.- Since:
- 1.1
- See Also:
-
Field Summary
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Constructor Summary
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Method Summary
Modifier and TypeMethodDescriptionclone()
Creates a copy of thisTimeZone
.static String[]
Gets all the available IDs supported.static String[]
getAvailableIDs
(int rawOffset) Gets the available IDs according to the given time zone offset in milliseconds.static TimeZone
Gets the defaultTimeZone
of the Java virtual machine.final String
Returns a long standard time name of thisTimeZone
suitable for presentation to the user in the default locale.final String
getDisplayName
(boolean daylight, int style) Returns a name in the specifiedstyle
of thisTimeZone
suitable for presentation to the user in the default locale.getDisplayName
(boolean daylight, int style, Locale locale) Returns a name in the specifiedstyle
of thisTimeZone
suitable for presentation to the user in the specifiedlocale
.final String
getDisplayName
(Locale locale) Returns a long standard time name of thisTimeZone
suitable for presentation to the user in the specifiedlocale
.int
Returns the amount of time to be added to local standard time to get local wall clock time.getID()
Gets the ID of this time zone.abstract int
getOffset
(int era, int year, int month, int day, int dayOfWeek, int milliseconds) Gets the time zone offset, for current date, modified in case of daylight savings.int
getOffset
(long date) Returns the offset of this time zone from UTC at the specified date.abstract int
Returns the amount of time in milliseconds to add to UTC to get standard time in this time zone.static TimeZone
getTimeZone
(String ID) Gets theTimeZone
for the given ID.static TimeZone
getTimeZone
(ZoneId zoneId) Gets theTimeZone
for the givenzoneId
.boolean
hasSameRules
(TimeZone other) Returns true if this zone has the same rule and offset as another zone.abstract boolean
inDaylightTime
(Date date) Queries if the givendate
is in Daylight Saving Time in this time zone.boolean
Returnstrue
if thisTimeZone
is currently in Daylight Saving Time, or if a transition from Standard Time to Daylight Saving Time occurs at any future time.static void
setDefault
(TimeZone zone) Sets theTimeZone
that is returned by thegetDefault
method.void
Sets the time zone ID.abstract void
setRawOffset
(int offsetMillis) Sets the base time zone offset to GMT.toZoneId()
Converts thisTimeZone
object to aZoneId
.abstract boolean
Queries if thisTimeZone
uses Daylight Saving Time.
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Field Details
-
SHORT
public static final int SHORTA style specifier forgetDisplayName()
indicating a short name, such as "PST."- Since:
- 1.2
- See Also:
-
LONG
public static final int LONGA style specifier forgetDisplayName()
indicating a long name, such as "Pacific Standard Time."- Since:
- 1.2
- See Also:
-
-
Constructor Details
-
TimeZone
public TimeZone()Sole constructor. (For invocation by subclass constructors, typically implicit.)
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Method Details
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getOffset
public abstract int getOffset(int era, int year, int month, int day, int dayOfWeek, int milliseconds) Gets the time zone offset, for current date, modified in case of daylight savings. This is the offset to add to UTC to get local time.This method returns a historically correct offset if an underlying
TimeZone
implementation subclass supports historical Daylight Saving Time schedule and GMT offset changes.- Parameters:
era
- the era of the given date.year
- the year in the given date.month
- the month in the given date. Month is 0-based. e.g., 0 for January.day
- the day-in-month of the given date.dayOfWeek
- the day-of-week of the given date.milliseconds
- the milliseconds in day in standard local time.- Returns:
- the offset in milliseconds to add to GMT to get local time.
- See Also:
-
getOffset
public int getOffset(long date) Returns the offset of this time zone from UTC at the specified date. If Daylight Saving Time is in effect at the specified date, the offset value is adjusted with the amount of daylight saving.This method returns a historically correct offset value if an underlying TimeZone implementation subclass supports historical Daylight Saving Time schedule and GMT offset changes.
- Parameters:
date
- the date represented in milliseconds since January 1, 1970 00:00:00 GMT- Returns:
- the amount of time in milliseconds to add to UTC to get local time.
- Since:
- 1.4
- See Also:
-
setRawOffset
public abstract void setRawOffset(int offsetMillis) Sets the base time zone offset to GMT. This is the offset to add to UTC to get local time.If an underlying
TimeZone
implementation subclass supports historical GMT offset changes, the specified GMT offset is set as the latest GMT offset and the difference from the known latest GMT offset value is used to adjust all historical GMT offset values.- Parameters:
offsetMillis
- the given base time zone offset to GMT.
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getRawOffset
public abstract int getRawOffset()Returns the amount of time in milliseconds to add to UTC to get standard time in this time zone. Because this value is not affected by daylight saving time, it is called raw offset.If an underlying
TimeZone
implementation subclass supports historical GMT offset changes, the method returns the raw offset value of the current date. In Honolulu, for example, its raw offset changed from GMT-10:30 to GMT-10:00 in 1947, and this method always returns -36000000 milliseconds (i.e., -10 hours).- Returns:
- the amount of raw offset time in milliseconds to add to UTC.
- See Also:
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getID
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setID
Sets the time zone ID. This does not change any other data in the time zone object.- Implementation Requirements:
- The default implementation throws a
NullPointerException
ifID
isnull
- Parameters:
ID
- the new time zone ID.- Throws:
NullPointerException
- This method may throw aNullPointerException
ifID
isnull
-
getDisplayName
Returns a long standard time name of thisTimeZone
suitable for presentation to the user in the default locale.This method is equivalent to:
getDisplayName(false,
LONG
, Locale.getDefault(Locale.Category.DISPLAY
));- Returns:
- the human-readable name of this time zone in the default locale.
- Since:
- 1.2
- See Also:
-
getDisplayName
Returns a long standard time name of thisTimeZone
suitable for presentation to the user in the specifiedlocale
.This method is equivalent to:
getDisplayName(false,
LONG
, locale);- Parameters:
locale
- the locale in which to supply the display name.- Returns:
- the human-readable name of this time zone in the given locale.
- Throws:
NullPointerException
- iflocale
isnull
.- Since:
- 1.2
- See Also:
-
getDisplayName
Returns a name in the specifiedstyle
of thisTimeZone
suitable for presentation to the user in the default locale. If the specifieddaylight
istrue
, a Daylight Saving Time name is returned (even if thisTimeZone
doesn't observe Daylight Saving Time). Otherwise, a Standard Time name is returned.This method is equivalent to:
getDisplayName(daylight, style, Locale.getDefault(
Locale.Category.DISPLAY
));- Parameters:
daylight
-true
specifying a Daylight Saving Time name, orfalse
specifying a Standard Time namestyle
- eitherLONG
orSHORT
- Returns:
- the human-readable name of this time zone in the default locale.
- Throws:
IllegalArgumentException
- ifstyle
is invalid.- Since:
- 1.2
- See Also:
-
getDisplayName
Returns a name in the specifiedstyle
of thisTimeZone
suitable for presentation to the user in the specifiedlocale
. If the specifieddaylight
istrue
, a Daylight Saving Time name is returned (even if thisTimeZone
doesn't observe Daylight Saving Time). Otherwise, a Standard Time name is returned.When looking up a time zone name, the default
Locale
search path ofResourceBundle
derived from the specifiedlocale
is used. (No fallbackLocale
search is performed.) If a time zone name in anyLocale
of the search path, includingLocale.ROOT
, is found, the name is returned. Otherwise, a string in the normalized custom ID format is returned.- Implementation Requirements:
- The default implementation throws an
IllegalArgumentException
ifstyle
is invalid or aNullPointerException
ifID
isnull
. - Parameters:
daylight
-true
specifying a Daylight Saving Time name, orfalse
specifying a Standard Time namestyle
- eitherLONG
orSHORT
locale
- the locale in which to supply the display name.- Returns:
- the human-readable name of this time zone in the given locale.
- Throws:
IllegalArgumentException
- This method may throw anIllegalArgumentException
ifstyle
is invalid.NullPointerException
- This method may throw aNullPointerException
ifID
isnull
- Since:
- 1.2
- See Also:
-
getDSTSavings
public int getDSTSavings()Returns the amount of time to be added to local standard time to get local wall clock time.The default implementation returns 3600000 milliseconds (i.e., one hour) if a call to
useDaylightTime()
returnstrue
. Otherwise, 0 (zero) is returned.If an underlying
TimeZone
implementation subclass supports historical and future Daylight Saving Time schedule changes, this method returns the amount of saving time of the last known Daylight Saving Time rule that can be a future prediction.If the amount of saving time at any given time stamp is required, construct a
Calendar
with thisTimeZone
and the time stamp, and callCalendar.get
(
Calendar.DST_OFFSET
)
.- Returns:
- the amount of saving time in milliseconds
- Since:
- 1.4
- See Also:
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useDaylightTime
public abstract boolean useDaylightTime()Queries if thisTimeZone
uses Daylight Saving Time.If an underlying
TimeZone
implementation subclass supports historical and future Daylight Saving Time schedule changes, this method refers to the last known Daylight Saving Time rule that can be a future prediction and may not be the same as the current rule. Consider callingobservesDaylightTime()
if the current rule should also be taken into account.- Returns:
true
if thisTimeZone
uses Daylight Saving Time,false
, otherwise.- See Also:
-
observesDaylightTime
public boolean observesDaylightTime()Returnstrue
if thisTimeZone
is currently in Daylight Saving Time, or if a transition from Standard Time to Daylight Saving Time occurs at any future time.The default implementation returns
true
ifuseDaylightTime()
orinDaylightTime(new Date())
returnstrue
.- Returns:
true
if thisTimeZone
is currently in Daylight Saving Time, or if a transition from Standard Time to Daylight Saving Time occurs at any future time;false
otherwise.- Since:
- 1.7
- See Also:
-
inDaylightTime
Queries if the givendate
is in Daylight Saving Time in this time zone.- Parameters:
date
- the given Date.- Returns:
true
if the given date is in Daylight Saving Time,false
, otherwise.- Throws:
NullPointerException
- This method may throw aNullPointerException
ifdate
isnull
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getTimeZone
Gets theTimeZone
for the given ID.- Parameters:
ID
- the ID for aTimeZone
, either an abbreviation such as "PST", a full name such as "America/Los_Angeles", or a custom ID such as "GMT-8:00". Note that the support of abbreviations is for JDK 1.1.x compatibility only and full names should be used.- Returns:
- the specified
TimeZone
, or the GMT zone if the given ID cannot be understood. - Throws:
NullPointerException
- ifID
isnull
-
getTimeZone
Gets theTimeZone
for the givenzoneId
.- Parameters:
zoneId
- aZoneId
from which the time zone ID is obtained- Returns:
- the specified
TimeZone
, or the GMT zone if the given ID cannot be understood. - Throws:
NullPointerException
- ifzoneId
isnull
- Since:
- 1.8
-
toZoneId
Converts thisTimeZone
object to aZoneId
.- Returns:
- a
ZoneId
representing the same time zone as thisTimeZone
- Since:
- 1.8
-
getAvailableIDs
Gets the available IDs according to the given time zone offset in milliseconds.- Parameters:
rawOffset
- the given time zone GMT offset in milliseconds.- Returns:
- an array of IDs, where the time zone for that ID has the specified GMT offset. For example, "America/Phoenix" and "America/Denver" both have GMT-07:00, but differ in daylight saving behavior.
- See Also:
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getAvailableIDs
Gets all the available IDs supported.- Returns:
- an array of IDs.
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getDefault
Gets the defaultTimeZone
of the Java virtual machine. If the cached defaultTimeZone
is available, its clone is returned. Otherwise, the method takes the following steps to determine the default time zone.- Use the
user.timezone
property value as the default time zone ID if it's available. - Detect the platform time zone ID. The source of the platform time zone and ID mapping may vary with implementation.
- Use
GMT
as the last resort if the given or detected time zone ID is unknown.
The default
TimeZone
created from the ID is cached, and its clone is returned. Theuser.timezone
property value is set to the ID upon return.- Returns:
- the default
TimeZone
- See Also:
- Use the
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setDefault
Sets theTimeZone
that is returned by thegetDefault
method.zone
is cached. Ifzone
is null, the cached defaultTimeZone
is cleared. This method doesn't change the value of theuser.timezone
property.- Parameters:
zone
- the new defaultTimeZone
, or null- See Also:
-
hasSameRules
Returns true if this zone has the same rule and offset as another zone. That is, if this zone differs only in ID, if at all. Returns false if the other zone is null.- Parameters:
other
- theTimeZone
object to be compared with- Returns:
- true if the other zone is not null and is the same as this one, with the possible exception of the ID
- Since:
- 1.2
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clone
-