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─────Run-Time Library───────────────────────────────────────────────────────
 
  Variable:  _daylight, _timezone, _tzname
 
  Include:   <time.h>
 
  Context:   _tzset
 
  Syntax:    int _daylight;
             long _timezone;
             char *_tzname[2];
 
     The _daylight, _timezone, and _tzname variables are used by
     several of the time and date functions to make local-time
     adjustments. They are declared in the include file TIME.H. The
     values of the variables are determined by the setting of an
     environment variable named TZ.
 
     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 GMT 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
 
     When you call the _ftime or localtime function, the values of
     these three variables are determined from the TZ setting. The
     _daylight variable is given a nonzero value if a DST zone is
     present in the TZ setting; otherwise, _daylight is 0.
 
     The _timezone variable is assigned the difference in seconds
     (calculated by converting the hours given in the TZ setting)
     between Universal Coordinated Time and local time. The first
     element of the _tzname variable is the string value of the
     three-letter time zone from the TZ setting; the second element
     is the string value of the DST zone. If the DST zone is omitted
     from the TZ setting, _tzname[1] is an empty string.
 
     The _ftime and localtime functions call another function, _tzset,
     to assign values to the three global variables from the TZ
     setting. You can also call _tzset directly if you like.
     See: _tzset
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