Sample_TZ_Specification

       EST5EDT4,M4.1.0,M10.5.0

     This sample TZ specification describes the rule defined in 1987
     for the Eastern time zone in the US:

     o  EST (Eastern Standard Time) is the designation for standard
        time, which is 5 hours behind UTC.

     o  EDT (Eastern Daylight Time) is the designation for summer
        time, which is 4 hours behind UTC. EDT starts on the first
        Sunday in April and ends on the last Sunday in October.

     Because time was not specified in either case, the changes
     occur at the default time, which is 2:00 A.M. The start and
     end dates did not need to be specified, because they are the
     defaults.