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  Variable:  daylight, timezone, tzname
 
  Include:   <time.h>
 
  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 Greenwich mean 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; for details, see
     tzset.