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_tzset
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─────Run-Time Library───────────────────────────────────────────────────────
The _tzset function uses the current setting of the environment
variable TZ to assign values to three global variables: _daylight,
_timezone, and _tzname. These variables are used by the _ftime and
localtime functions to make corrections from Universal Coordinated
Time (UCT) to local time, and by the time function to compute UCT
from system time.
Use the following syntax to set the TZ environment variable:
set TZ=tzn[+│-]hh[:mm[:ss]][dzn]
The <tzn> argument must be a three-letter time-zone name, such as
PST, followed by an optionally signed number, [+│-]<hh>, giving
the difference in hours between UCT and local time. The hours can
be optionally followed by minutes, :<mm>; seconds, :<ss>; and a
three-letter daylight-saving-time (DST) zone, such as PDT. For
example, PST8PDT represents a valid TZ value for the Pacific time
zone.
Separate hours, minutes, and seconds with colons (:). If DST is
never in effect, as is the case in certain states and localities,
TZ should be set without a <dzn> zone.
If TZ is not currently set, the default is PST8PDT, which
corresponds to the Pacific time zone.
Based on the TZ environment variable, the following values are
assigned to the _daylight, _timezone, and _tzname variables when
_tzset is called:
Variable Value
_daylight Nonzero value if a daylight-saving-time zone is
specified in the TZ setting; otherwise, 0
_timezone The difference in seconds between UCT and local time
_tzname[0] The string value of the three-letter time-zone name
from the TZ setting
_tzname[1] The string value of the daylight-saving-time zone,
or an empty string if the daylight-saving-time
zone is omitted from the TZ setting
The default for _daylight is 1; for _timezone, 28800; for
_tzname[0], PST; and for _tzname[1], PDT. This corresponds to
PST8PDT.
If the DST zone is omitted from the TZ settings, the _daylight
variable will be 0 and the _ftime, gmtime, and localtime functions
will return 0 for their DST flags.
Return Value
None.
-♦-