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The array tzname contains two strings, which are the standard
three-letter names of the pair of time zones (standard and daylight
savings) 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 savings time is in use (for
example, "EDT"). These correspond to the std and dst
strings (respectively) from the TZ environment variable.
The tzname array is initialized from the TZ environment
variable whenever tzset, ctime, strftime,
mktime, or localtime is called.
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. These variables are set by calling localtime.
This contains the difference between GMT and local standard time, in
seconds. For example, in the U.S. Eastern time zone, the value is
5*60*60.
This variable has a nonzero value if the standard U.S. daylight savings time rules apply.
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