java.util
Class TimeZone

java.lang.Object
  |
  +--java.util.TimeZone
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 Pacific Standard Time zone is "PST". So, you can get a PST TimeZone object with: 

 TimeZone tz = TimeZone.getTimeZone("PST");
You can use 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 you can create a custom time zone ID with the following syntax: 
 GMT[+|-]hh[[:]mm]
For example, you might specify GMT+14:00 as a custom time zone ID. The TimeZone that is returned when you specify a custom time zone ID does not include daylight savings time.

See Also:
Calendar, GregorianCalendar, SimpleTimeZone, Serialized Form

Field Summary
private static Hashtable cachedLocaleData
          Cache to hold the SimpleDateFormat objects for a Locale.
private static String CUSTOM_ID
           
private static TimeZone defaultZone
           
private static TimeZone GMT
           
(package private) static String GMT_ID
           
private static int GMT_ID_LENGTH
           
private  String ID
          The string identifier of this TimeZone.
static int LONG
          A style specifier for getDisplayName() indicating a long name, such as "Pacific Standard Time."
private static java.text.NumberFormat numberFormat
           
private static int ONE_DAY
           
private static int ONE_HOUR
           
private static int ONE_MINUTE
           
(package private) static long serialVersionUID
           
static int SHORT
          A style specifier for getDisplayName() indicating a short name, such as "PST."
 
Constructor Summary
TimeZone()
          Sole constructor.
 
Method Summary
 Object clone()
          Overrides Cloneable
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.
static TimeZone getDefault()
          Gets the default TimeZone for this host.
 String getDisplayName()
          Returns a name of this time zone suitable for presentation to the user in the default locale.
 String getDisplayName(boolean daylight, int style)
          Returns a name of this time zone suitable for presentation to the user in the default locale.
 String getDisplayName(boolean daylight, int style, Locale locale)
          Returns a name of this time zone suitable for presentation to the user in the specified locale.
 String getDisplayName(Locale locale)
          Returns a name of this time zone suitable for presentation to the user in the specified locale.
 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.
(package private)  int getOffset(int era, int year, int month, int day, int dayOfWeek, int milliseconds, int monthLength)
          Gets the time zone offset, for current date, modified in case of daylight savings.
abstract  int getRawOffset()
          Gets unmodified offset, NOT modified in case of daylight savings.
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 savings time in this time zone.
private static SimpleTimeZone parseCustomTimeZone(String id)
          Parse a custom time zone identifier and return a corresponding zone.
static void setDefault(TimeZone zone)
          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 time zone uses daylight savings time.
 
Methods inherited from class java.lang.Object
, equals, finalize, getClass, hashCode, notify, notifyAll, registerNatives, toString, wait, wait, wait
 

Field Detail

SHORT

public static final int SHORT
A style specifier for getDisplayName() indicating a short name, such as "PST."
See Also:
LONG

LONG

public static final int LONG
A style specifier for getDisplayName() indicating a long name, such as "Pacific Standard Time."
See Also:
SHORT

ONE_MINUTE

private static final int ONE_MINUTE

ONE_HOUR

private static final int ONE_HOUR

ONE_DAY

private static final int ONE_DAY

cachedLocaleData

private static Hashtable cachedLocaleData
Cache to hold the SimpleDateFormat objects for a Locale.

serialVersionUID

static final long serialVersionUID

ID

private String ID
The string identifier of this TimeZone. This is a programmatic identifier used internally to look up TimeZone objects from the system table and also to map them to their localized display names. ID values are unique in the system table but may not be for dynamically created zones.

defaultZone

private static TimeZone defaultZone

GMT_ID

static final String GMT_ID

GMT_ID_LENGTH

private static final int GMT_ID_LENGTH

CUSTOM_ID

private static final String CUSTOM_ID

numberFormat

private static java.text.NumberFormat numberFormat

GMT

private static final TimeZone GMT
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.
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 millis in day in standard local time.
Returns:
the offset to add *to* GMT to get local time.

getOffset

int getOffset(int era,
              int year,
              int month,
              int day,
              int dayOfWeek,
              int milliseconds,
              int monthLength)
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.
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 millis in day in standard local time.
monthLength - the length of the given month in days.
Returns:
the offset to add *to* GMT to get local time.

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.
Parameters:
offsetMillis - the given base time zone offset to GMT.

getRawOffset

public abstract int getRawOffset()
Gets unmodified offset, NOT modified in case of daylight savings. This is the offset to add *to* UTC to get local time.
Returns:
the unmodified offset to add *to* UTC to get local time.

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 name of this time zone suitable for presentation to the user in the default locale. This method returns the long name, not including daylight savings. If the display name is not available for the locale, then this method returns a string in the format GMT[+-]hh:mm.
Returns:
the human-readable name of this time zone in the default locale.

getDisplayName

public final String getDisplayName(Locale locale)
Returns a name of this time zone suitable for presentation to the user in the specified locale. This method returns the long name, not including daylight savings. If the display name is not available for the locale, then this method returns a string in the format GMT[+-]hh:mm.
Parameters:
locale - the locale in which to supply the display name.
Returns:
the human-readable name of this time zone in the given locale or in the default locale if the given locale is not recognized.

getDisplayName

public final String getDisplayName(boolean daylight,
                                   int style)
Returns a name of this time zone suitable for presentation to the user in the default locale. If the display name is not available for the locale, then this method returns a string in the format GMT[+-]hh:mm.
Parameters:
daylight - if true, return the daylight savings name.
style - either LONG or SHORT
Returns:
the human-readable name of this time zone in the default locale.

getDisplayName

public String getDisplayName(boolean daylight,
                             int style,
                             Locale locale)
Returns a name of this time zone suitable for presentation to the user in the specified locale. If the display name is not available for the locale, then this method returns a string in the format GMT[+-]hh:mm.
Parameters:
daylight - if true, return the daylight savings name.
style - either LONG or SHORT
locale - the locale in which to supply the display name.
Returns:
the human-readable name of this time zone in the given locale or in the default locale if the given locale is not recognized.
Throws:
IllegalArgumentException - style is invalid.

useDaylightTime

public abstract boolean useDaylightTime()
Queries if this time zone uses daylight savings time.
Returns:
true if this time zone uses daylight savings time, false, otherwise.

inDaylightTime

public abstract boolean inDaylightTime(Date date)
Queries if the given date is in daylight savings time in this time zone.
Parameters:
date - the given Date.
Returns:
true if the given date is in daylight savings time, false, otherwise.

getTimeZone

public static 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".
Returns:
the specified TimeZone, or the GMT zone if the given ID cannot be understood.

getAvailableIDs

public static String[] getAvailableIDs(int rawOffset)
Gets the available IDs according to the given time zone offset.
Parameters:
rawOffset - the given time zone GMT offset.
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 savings behavior.

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 for this host. The source of the default TimeZone may vary with implementation.
Returns:
a default TimeZone.

setDefault

public static void setDefault(TimeZone zone)
Sets the TimeZone that is returned by the getDefault method.
Parameters:
zone - the new default time zone

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.
Parameters:
other - the TimeZone object to be compared with
Returns:
true if the given zone is the same as this one, with the possible exception of the ID

clone

public Object clone()
Overrides Cloneable
Overrides:
clone in class Object

parseCustomTimeZone

private static final SimpleTimeZone parseCustomTimeZone(String id)
Parse a custom time zone identifier and return a corresponding zone.
Parameters:
id - a string of the form GMT[+-]hh:mm, GMT[+-]hhmm, or GMT[+-]hh.
Returns:
a newly created SimpleTimeZone with the given offset and no daylight savings time, or null if the id cannot be parsed.