(libc.info.gz) Time Zone Functions

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(libc.info.gz) TZ Variable

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 21.4.8 Functions and Variables for Time Zones
 ---------------------------------------------
 
  -- Variable: char * tzname [2]
      The array `tzname' contains two strings, which are the standard
      names of the pair of time zones (standard and Daylight Saving)
      that the user has selected.  `tzname[0]' is the name of the
      standard time zone (for example, `"EST"'), and `tzname[1]' is the
      name for the time zone when Daylight Saving Time is in use (for
      example, `"EDT"').  These correspond to the STD and DST strings
      (respectively) from the `TZ' environment variable.  If Daylight
      Saving Time is never used, `tzname[1]' is the empty string.
 
      The `tzname' array is initialized from the `TZ' environment
      variable whenever `tzset', `ctime', `strftime', `mktime', or
      `localtime' is called.  If multiple abbreviations have been used
      (e.g. `"EWT"' and `"EDT"' for U.S. Eastern War Time and Eastern
      Daylight Time), the array contains the most recent abbreviation.
 
      The `tzname' array is required for POSIX.1 compatibility, but in
      GNU programs it is better to use the `tm_zone' member of the
      broken-down time structure, since `tm_zone' reports the correct
      abbreviation even when it is not the latest one.
 
      Though the strings are declared as `char *' the user must refrain
      from modifying these strings.  Modifying the strings will almost
      certainly lead to trouble.
 
 
  -- Function: void tzset (void)
      The `tzset' function initializes the `tzname' variable from the
      value of the `TZ' environment variable.  It is not usually
      necessary for your program to call this function, because it is
      called automatically when you use the other time conversion
      functions that depend on the time zone.
 
    The following variables are defined for compatibility with System V
 Unix.  Like `tzname', these variables are set by calling `tzset' or the
 other time conversion functions.
 
  -- Variable: long int timezone
      This contains the difference between UTC and the latest local
      standard time, in seconds west of UTC.  For example, in the U.S.
      Eastern time zone, the value is `5*60*60'.  Unlike the `tm_gmtoff'
      member of the broken-down time structure, this value is not
      adjusted for daylight saving, and its sign is reversed.  In GNU
      programs it is better to use `tm_gmtoff', since it contains the
      correct offset even when it is not the latest one.
 
  -- Variable: int daylight
      This variable has a nonzero value if Daylight Saving Time rules
      apply.  A nonzero value does not necessarily mean that Daylight
      Saving Time is now in effect; it means only that Daylight Saving
      Time is sometimes in effect.
 

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(libc.info.gz) TZ Variable

(libc.info.gz) Calendar Time

(libc.info.gz) Time Functions Example