The local time zone is obtained from, in order of
preference: 1) the user defaults
database: NSGlobalDomain "Local Time Zone"
2) the GNUSTEP_TZ environment variable 3) the
file "localtime" in
System/Library/Libraries/Resources/NSTimeZone
4) the TZ environment variable 5) The
system zone settings (typically in /etc/localtime)
6) tzset and tznam on platforms which have it
7) Windows registry, on Win32 systems
8) or the fallback time zone (which is UTC)
If the GNUstep time zone datafiles become too out of
date, one can download an updated database from
ftp://elsie.nci.nih.gov/pub/
and compile it as specified in the README file in the
NSTimeZones directory.
Time zone names in NSDates should be GMT, MET etc. not
Europe/Berlin, America/Washington etc.
The problem with this is that various time zones may
use the same abbreviation (e.g. Australia/Brisbane and
America/New_York both use EST), and some
time zones may have different rules for daylight
saving time even if the abbreviation and offsets
from UTC are the same.
The problems with depending on the OS for providing
time zone info are that time zone names may vary
wildly between OSes (this could be a big problem
when archiving is used between different systems).
Win32: Time zone names read from the registry are
different from other GNUstep installations. Be
careful when moving data between platforms in this
case.
Returns a dictionary containing time zone
abbreviations and their corresponding time
zone names. More than one time zone may be associated
with a single abbreviation. In this case, the
dictionary contains only one (usually the most
common) time zone name for the abbreviation.
Returns an array of all the known regions.
There are 24 elements, of course, one for each time
zone. Each element contains an array of NSStrings
which are the region names.
Return a timezone for the specified offset from GMT.
The timezone returned does not use
daylight savings time. The actual timezone
returned has an offset rounded to the nearest
minute. Time zones with an offset of more
than +/- 18 hours are disallowed, and nil
is returned.
Returns a timezone for the specified
abbreviation. The same abbreviations are
used in different regions so this isn't particularly
useful. Calls NSTimeZone-abbreviation
dictionary an so uses a lot of memory.
Initialises a time zone object using the
supplied data object. This
method is intended for internal use by the
NSTimeZone class cluster. Don't use it... use
-initWithName:
instead.
Returns the number of seconds by which the receiver
differs from Greenwich Mean Time at the date
aDate. If the time zone uses
daylight savings time, the returned value will
vary at different times of year.
Availability: OPENSTEP 4.0.0 removed at MacOS-X 10.0.0
This class serves no useful purpose in GNUstep other
than to provide a backup mechanism for handling
abbreviations where the precomputed data files
cannot be found. It is provided primarily for backward
compatibility with the OpenStep spec. It is
missing entirely from MacOS-X.