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     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 Greenwich mean time
     (GMT) to local time, and by the time function to compute GMT from
     system time.
 
     The value of the environment variable TZ must be a three-letter
     time-zone name, such as PST, followed by an optionally signed
     number giving the difference in hours between GMT and local time.
     The number can be followed by a three-letter daylight-saving-time
     (DST) zone, such as PDT. For example, "PST8PDT" represents a valid
     TZ value for the Pacific time zone. If DST is never in effect, as
     is the case in certain states and localities, TZ should be set
     without a DST 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 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
 
     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.
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