java.util

## 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 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.
  Since:
    JDK1.1
  Author:
    Mark Davis, David Goldsmith, Chen-Lieh Huang, Alan Liu
  See Also:
    `Calendar`, `GregorianCalendar`, `SimpleTimeZone`, Serialized Form

- - ### Field Summary

    Fields
    Modifier and Type | Field and Description
    --- | ---
    `static int` | `LONG` A style specifier for `getDisplayName()` indicating a long name, such as "Pacific Standard Time."
    `static int` | `SHORT` A style specifier for `getDisplayName()` indicating a short name, such as "PST."

  - ### Constructor Summary

    Constructors
    Constructor and Description
    `TimeZone()` Sole constructor.

  - ### Method Summary

    All Methods Static Methods Instance Methods Abstract Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `Object` | `clone()` Creates a copy of this `TimeZone`.
    `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 `TimeZone` for this host.
    `String` | `getDisplayName()` Returns a long standard time name of this `TimeZone` suitable for presentation to the user in the default locale.
    `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.
    `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`.
    `String` | `getDisplayName(Locale locale)` Returns a long standard time name of this `TimeZone` suitable for presentation to the user in the specified `locale`.
    `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 `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.
    `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 `TimeZone` uses Daylight Saving Time.

    - ### Methods inherited from 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` - if `locale` is `null`.
      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, 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.
      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, or `false` specifying a Standard Time 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.
      Throws:
        `IllegalArgumentException` - if `style` is invalid.
        `NullPointerException` - if `locale` is `null`.
      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 this `TimeZone` 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 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.
      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 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.

    - #### 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` for this host. The source of the default `TimeZone` may vary with implementation.
      Returns:
        a default `TimeZone`.
      See Also:
        `setDefault(java.util.TimeZone)`

    - #### setDefault

          public static void setDefault(TimeZone zone)

      Sets the `TimeZone` that is returned by the `getDefault` method. If `zone` is null, reset the default to the value it had originally when the VM first started.
      Parameters:
        `zone` - the new default time zone
      See Also:
        `getDefault()`

    - #### 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` - 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
      Since:
        1.2

    - #### clone

          public Object clone()

      Creates a copy of this `TimeZone`.
      Overrides:
        `clone` in class `Object`
      Returns:
        a clone of this `TimeZone`
      See Also:
        `Cloneable`

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