TimeZone

public abstract class TimeZone extends Object
implements Serializable Cloneable

Known Direct Subclasses SimpleTimeZone SimpleTimeZone SimpleTimeZone is a concrete subclass of TimeZone that represents a time zone for use with a Gregorian calendar.

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:

 TimeZone tz = TimeZone.getTimeZone("America/Los_Angeles");
 

You can use the 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:

 CustomID:
         GMT Sign Hours : Minutes
         GMT Sign Hours Minutes
         GMT Sign Hours
 Sign: one of
         + -
 Hours:
         Digit
         Digit Digit
 Minutes:
         Digit Digit
 Digit: one of
         0 1 2 3 4 5 6 7 8 9
 

Hours must be between 0 to 23 and Minutes must be between 00 to 59. For example, "GMT+10" and "GMT+0010" mean ten hours and ten minutes ahead of GMT, respectively.

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:

 NormalizedCustomID:
         GMT Sign TwoDigitHours : Minutes
 Sign: one of
         + -
 TwoDigitHours:
         Digit Digit
 Minutes:
         Digit Digit
 Digit: one of
         0 1 2 3 4 5 6 7 8 9
 

For example, TimeZone.getTimeZone("GMT-8").getID() returns "GMT-08:00".

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.

See Also

• Calendar
• GregorianCalendar
• SimpleTimeZone

Constant Summary

int	LONG	A style specifier for getDisplayName() indicating a long name, such as "Pacific Standard Time."
int	SHORT	A style specifier for getDisplayName() indicating a short name, such as "PST."

Public Constructor Summary

TimeZone() Sole constructor.

Public Method Summary

Object	clone() Creates a copy of this TimeZone.
synchronized static String[]	getAvailableIDs() Gets all the available IDs supported.
synchronized static String[]	getAvailableIDs(int rawOffset) Gets the available IDs according to the given time zone offset in milliseconds.
int	getDSTSavings() Returns the amount of time to be added to local standard time to get local wall clock time.
static TimeZone	getDefault() Gets the default TimeZone for this host.
String	getDisplayName(boolean daylightTime, int style, Locale locale) Returns the short or long name of this time zone with either standard or daylight time, as written in locale.
final String	getDisplayName(Locale locale) Returns a long standard time name of this TimeZone suitable for presentation to the user in the specified locale.
final String	getDisplayName(boolean daylight, int style) Returns a name in the specified style of this TimeZone suitable for presentation to the user in the default locale.
final String	getDisplayName() Returns a long standard time name of this TimeZone suitable for presentation to the user in the default locale.
String	getID() Gets the ID of this time zone.
int	getOffset(long date) Returns the offset of this time zone from UTC at the specified date.
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.
abstract int	getRawOffset() Returns the amount of time in milliseconds to add to UTC to get standard time in this time zone.
synchronized static TimeZone	getTimeZone(String id) Gets the TimeZone for the given ID.
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 given date is in Daylight Saving Time in this time zone.
boolean	observesDaylightTime() Returns true if this TimeZone is currently in Daylight Saving Time, or if a transition from Standard Time to Daylight Saving Time occurs at any future time.
synchronized static void	setDefault(TimeZone timeZone) Sets the TimeZone that is returned by the getDefault method.
void	setID(String ID) Sets the time zone ID.
abstract void	setRawOffset(int offsetMillis) Sets the base time zone offset to GMT.
abstract boolean	useDaylightTime() Queries if this TimeZone uses Daylight Saving Time.

Inherited Method Summary

From class java.lang.Object

Object	clone() Creates and returns a copy of this Object.
boolean	equals(Object obj) Compares this instance with the specified object and indicates if they are equal.
void	finalize() Invoked when the garbage collector has detected that this instance is no longer reachable.
final Class<?>	getClass() Returns the unique instance of Class that represents this object's class.
int	hashCode() Returns an integer hash code for this object.
final void	notify() Causes a thread which is waiting on this object's monitor (by means of calling one of the wait() methods) to be woken up.
final void	notifyAll() Causes all threads which are waiting on this object's monitor (by means of calling one of the wait() methods) to be woken up.
String	toString() Returns a string containing a concise, human-readable description of this object.
final void	wait(long timeout, int nanos) Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object or until the specified timeout expires.
final void	wait(long timeout) Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object or until the specified timeout expires.
final void	wait() Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object.

Constants

public static final int LONG

A style specifier for getDisplayName() indicating a long name, such as "Pacific Standard Time."

See Also

• SHORT

Constant Value: 1

public static final int SHORT

A style specifier for getDisplayName() indicating a short name, such as "PST."

See Also

• LONG

Constant Value: 0

Public Constructors

public TimeZone ()

Sole constructor. (For invocation by subclass constructors, typically implicit.)

Public Methods

public Object clone ()

Creates a copy of this TimeZone.

Returns

• a clone of this TimeZone

public static synchronized String[] getAvailableIDs ()

Gets all the available IDs supported.

Returns

• an array of IDs.

public static synchronized String[] getAvailableIDs (int rawOffset)

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

• getRawOffset()

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() returns true. 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 this TimeZone and the time stamp, and call Calendar.get(Calendar.DST_OFFSET).

Returns

• the amount of saving time in milliseconds

See Also

• inDaylightTime(Date)
• getOffset(long)
• getOffset(int, int, int, int, int, int)
• Calendar.ZONE_OFFSET

public static TimeZone getDefault ()

Gets the default TimeZone for this host. The source of the default TimeZone may vary with implementation.

Returns

• a default TimeZone.

See Also

• setDefault(TimeZone)

public String getDisplayName (boolean daylightTime, int style, Locale locale)

Returns the short or long name of this time zone with either standard or daylight time, as written in locale. If the name is not available, the result is in the format GMT[+-]hh:mm.

Parameters

daylightTime	true for daylight time, false for standard time.
style	either LONG or SHORT.
locale	the display locale.

public final String getDisplayName (Locale locale)

Returns a long standard time name of this TimeZone suitable for presentation to the user in the specified locale.

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	if locale is null.

See Also

• getDisplayName(boolean, int, Locale)

public final String getDisplayName (boolean daylight, int style)

Returns a name in the specified style of this TimeZone suitable for presentation to the user in the default locale. If the specified daylight is true, a Daylight Saving Time name is returned (even if this TimeZone 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, or false specifying a Standard Time name
style	either LONG or SHORT

Returns

• the human-readable name of this time zone in the default locale.

Throws

IllegalArgumentException	if style is invalid.

See Also

• getDisplayName(boolean, int, Locale)
• Locale.getDefault(Locale.Category)
• Locale.Category
• DateFormatSymbols.getZoneStrings()

public final String getDisplayName ()

Returns a long standard time name of this TimeZone 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.

See Also

• getDisplayName(boolean, int, Locale)
• Locale.getDefault(Locale.Category)
• Locale.Category

public String getID ()

Gets the ID of this time zone.

Returns

• the ID of this time zone.

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.

See Also

• Calendar.ZONE_OFFSET
• Calendar.DST_OFFSET

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

• Calendar.ZONE_OFFSET
• Calendar.DST_OFFSET

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

• Calendar.ZONE_OFFSET

public static synchronized TimeZone getTimeZone (String id)

Gets the TimeZone for the given ID.

Parameters

id	the ID for a TimeZone, 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.

public boolean hasSameRules (TimeZone other)

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	the TimeZone 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

public abstract boolean inDaylightTime (Date date)

Queries if the given date 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.

public boolean observesDaylightTime ()

Returns true if this TimeZone 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 if useDaylightTime() or inDaylightTime(new Date()) returns true.

Returns

• true if this TimeZone is currently in Daylight Saving Time, or if a transition from Standard Time to Daylight Saving Time occurs at any future time; false otherwise.

See Also

• useDaylightTime()
• inDaylightTime(Date)
• Calendar.DST_OFFSET

public static synchronized void setDefault (TimeZone timeZone)

Sets the TimeZone that is returned by the getDefault method. timeZone is cached. If timeZone is null, the cached default TimeZone is cleared. This method doesn't change the value of the user.timezone property.

Parameters

timeZone	the new default TimeZone, or null

See Also

• getDefault()

public void setID (String ID)

Sets the time zone ID. This does not change any other data in the time zone object.

Parameters

ID	the new time zone ID.

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.

public abstract boolean useDaylightTime ()

Queries if this TimeZone 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 calling observesDaylightTime() if the current rule should also be taken into account.

Returns

• true if this TimeZone uses Daylight Saving Time, false, otherwise.

See Also

• inDaylightTime(Date)
• Calendar.DST_OFFSET