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Class std.datetime.timezone.PosixTimeZone

Represents a time zone from a TZ Database time zone file. Files from the TZ Database are how Posix systems hold their time zone information. Unfortunately, Windows does not use the TZ Database. To use the TZ Database, use PosixTimeZone (which reads its information from the TZ Database files on disk) on Windows by providing the TZ Database files and telling PosixTimeZone.getTimeZone where the directory holding them is.

class PosixTimeZone
  : TimeZone ;

To get a PosixTimeZone, call PosixTimeZone.getTimeZone (which allows specifying the location the time zone files).


hasDST[get] boolWhether this time zone has Daylight Savings Time at any point in time. Note that for some time zone types it may not have DST for current dates but will still return true for hasDST because the time zone did at some point have DST.
dstName[get] stringTypically, the abbreviation (generally 3 or 4 letters) for the time zone when DST is in effect (e.g. PDT). It is not necessarily unique.
name[get] stringThe name of the time zone. Exactly how the time zone name is formatted depends on the derived class. In the case of PosixTimeZone, it's the TZ Database name, whereas with WindowsTimeZone, it's the name that Windows chose to give the registry key for that time zone (typically the name that they give stdTime if the OS is in English). For other time zone types, what it is depends on how they're implemented.
stdName[get] stringTypically, the abbreviation (generally 3 or 4 letters) for the time zone when DST is not in effect (e.g. PST). It is not necessarily unique.


dstInEffect (stdTime) Takes the number of hnsecs (100 ns) since midnight, January 1st, 1 A.D. in UTC time (i.e. std time) and returns whether DST is in effect in this time zone at the given point in time.
getInstalledTZNames (subName, tzDatabaseDir) Returns a list of the names of the time zones installed on the system.
getTimeZone (name, tzDatabaseDir) Returns a TimeZone with the give name per the TZ Database. The time zone information is fetched from the TZ Database time zone files in the given directory.
tzToUTC (adjTime) Takes the number of hnsecs (100 ns) since midnight, January 1st, 1 A.D. in this time zone's time and converts it to UTC (i.e. std time).
utcToTZ (stdTime) Takes the number of hnsecs (100 ns) since midnight, January 1st, 1 A.D. in UTC time (i.e. std time) and converts it to this time zone's time.
factory (classname) Create instance of class specified by the fully qualified name classname. The class must either have no constructors or have a default constructor.
opCmp (o) Compare with another Object obj.
opEquals (o) Test whether this is equal to o. The default implementation only compares by identity (using the is operator). Generally, overrides and overloads for opEquals should attempt to compare objects by their contents. A class will most likely want to add an overload that takes your specific type as the argument and does the content comparison. Then you can override this and forward it to your specific typed overload with a cast. Remember to check for null on the typed overload.
toHash () Compute hash function for Object.
toString () Convert Object to a human readable string.
utcOffsetAt (stdTime) Returns what the offset from UTC is at the given std time. It includes the DST offset in effect at that time (if any).


Unless your system's local time zone deals with leap seconds (which is highly unlikely), then the only way to get a time zone which takes leap seconds into account is to use PosixTimeZone with a time zone whose name starts with "right/". Those time zone files do include leap seconds, and PosixTimeZone will take them into account (though posix systems which use a "right/" time zone as their local time zone will not take leap seconds into account even though they're in the file).

See Also

Home of the TZ Database files
Wikipedia entry on TZ Database
List of Time Zones


Jonathan M Davis


Boost License 1.0.