'SYSTEM', value )

   Note that such a call has the side effect of setting the value
   associated with ZONE to a blank.

   Zone
   -----

   You may alter the UTC system by specifying a time zone (UTC
   offset). For example you may specify that epochs are referred
   to Pacific Standard Time (PST --- UTC-7). The standard
   abbreviations for U.S. time zones are recognized:

      EST   UTC-5
      EDT   UTC-4
      CST   UTC-6
      CDT   UTC-5
      MST   UTC-7
      MDT   UTC-6
      PST   UTC-8
      