Class TimeZone
- java.lang.Object
-
- java.util.TimeZone
- All Implemented Interfaces:
-
Serializable
,Cloneable
- Direct Known Subclasses:
SimpleTimeZone
public abstract class TimeZone extends Object implements Serializable, Cloneable
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 9Hours 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 9For 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.- Since:
- 1.1
- See Also:
-
Calendar
,GregorianCalendar
,SimpleTimeZone
, Serialized Form
Field Summary
Modifier and Type | Field | Description |
---|---|---|
static int | LONG | A style specifier for |
static int | SHORT | A style specifier for |
Constructor Summary
Constructor | Description |
---|---|
TimeZone() | Sole constructor. |
Method Summary
Modifier and Type | Method | Description |
---|---|---|
Object | clone() | Creates a copy of this |
static String[] | getAvailableIDs() | 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 | getDefault() | Gets the default |
String | getDisplayName() | Returns a long standard time name of this |
String | getDisplayName(boolean daylight,
int style) | Returns a name in the specified |
String | getDisplayName(boolean daylight,
int style,
Locale locale) | Returns a name in the specified |
String | getDisplayName(Locale locale) | Returns a long standard time name of this |
int | getDSTSavings() | Returns the amount of time to be added to local standard time to get local wall clock time. |
String | 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 | getRawOffset() | 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 the |
static TimeZone | getTimeZone(ZoneId zoneId) | Gets the |
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 |
boolean | observesDaylightTime() | Returns |
static void | setDefault(TimeZone zone) | Sets the |
void | setID(String ID) | Sets the time zone ID. |
abstract void | setRawOffset(int offsetMillis) | Sets the base time zone offset to GMT. |
ZoneId | toZoneId() | Converts this |
abstract boolean | useDaylightTime() | Queries if this |
Methods declared in class java.lang.Object
equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
Field Detail
SHORT
public static final int SHORT
A style specifier for getDisplayName()
indicating a short name, such as "PST."
- Since:
- 1.2
- See Also:
-
LONG
, Constant Field Values
LONG
public static final int LONG
A style specifier for getDisplayName()
indicating a long name, such as "Pacific Standard Time."
- Since:
- 1.2
- See Also:
-
SHORT
, Constant Field Values
Constructor Detail
TimeZone
public TimeZone()
Sole constructor. (For invocation by subclass constructors, typically implicit.)
Method Detail
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:
-
Calendar.ZONE_OFFSET
,Calendar.DST_OFFSET
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:
-
Calendar.ZONE_OFFSET
,Calendar.DST_OFFSET
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.
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:
Calendar.ZONE_OFFSET
getID
public String getID()
Gets the ID of this time zone.
- Returns:
- the ID of this time zone.
setID
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.
getDisplayName
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.
- Since:
- 1.2
- See Also:
-
getDisplayName(boolean, int, Locale)
,Locale.getDefault(Locale.Category)
,Locale.Category
getDisplayName
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
- iflocale
isnull
. - Since:
- 1.2
- See Also:
getDisplayName(boolean, int, Locale)
getDisplayName
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, orfalse
specifying a Standard Time name -
style
- 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(boolean, int, Locale)
,Locale.getDefault(Locale.Category)
,Locale.Category
,DateFormatSymbols.getZoneStrings()
getDisplayName
public String getDisplayName(boolean daylight, int style, Locale locale)
Returns a name in the specified style
of this TimeZone
suitable for presentation to the user in the specified
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.
When looking up a time zone name, the default Locale
search path of ResourceBundle
derived from the specified locale
is used. (No fallback Locale
search is performed.) If a time zone name in any Locale
of the search path, including Locale.ROOT
, is found, the name is returned. Otherwise, a string in the normalized custom ID format is returned.
- Parameters:
-
daylight
-true
specifying a Daylight Saving Time name, orfalse
specifying a Standard Time name -
style
- 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
- ifstyle
is invalid. -
NullPointerException
- iflocale
isnull
. - Since:
- 1.2
- See Also:
DateFormatSymbols.getZoneStrings()
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()
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
- Since:
- 1.4
- See Also:
-
inDaylightTime(Date)
,getOffset(long)
,getOffset(int,int,int,int,int,int)
,Calendar.ZONE_OFFSET
useDaylightTime
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 thisTimeZone
uses Daylight Saving Time,false
, otherwise. - See Also:
-
inDaylightTime(Date)
,Calendar.DST_OFFSET
observesDaylightTime
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 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:
-
useDaylightTime()
,inDaylightTime(Date)
,Calendar.DST_OFFSET
inDaylightTime
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.
getTimeZone
public static TimeZone getTimeZone(String ID)
Gets the TimeZone
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.
getTimeZone
public static TimeZone getTimeZone(ZoneId zoneId)
Gets the TimeZone
for the given zoneId
.
- 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
public ZoneId toZoneId()
Converts this TimeZone
object to a ZoneId
.
- Returns:
- a
ZoneId
representing the same time zone as thisTimeZone
- Since:
- 1.8
getAvailableIDs
public static 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()
getAvailableIDs
public static String[] getAvailableIDs()
Gets all the available IDs supported.
- Returns:
- an array of IDs.
getDefault
public static TimeZone getDefault()
Gets the default TimeZone
of the Java virtual machine. If the cached default TimeZone
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. The user.timezone
property value is set to the ID upon return.
- Returns:
- the default
TimeZone
- See Also:
setDefault(TimeZone)
setDefault
public static void setDefault(TimeZone zone)
Sets the TimeZone
that is returned by the getDefault
method. zone
is cached. If zone
is null, the cached default TimeZone
is cleared. This method doesn't change the value of the user.timezone
property.
- Parameters:
-
zone
- the new defaultTimeZone
, or null - Throws:
-
SecurityException
- if the security manager'scheckPermission
deniesPropertyPermission("user.timezone", "write")
- See Also:
-
getDefault()
,PropertyPermission
hasSameRules
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
- 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
clone
public Object clone()
Creates a copy of this TimeZone
.