.. function:: tzset()
- Resets the time conversion rules used by the library routines. The environment
- variable :envvar:`TZ` specifies how this is done.
+ Reset the time conversion rules used by the library routines. The environment
+ variable :envvar:`TZ` specifies how this is done. It will also set the variables
+ ``tzname`` (from the :envvar:`TZ` environment variable), ``timezone`` (non-DST
+ seconds West of UTC), ``altzone`` (DST seconds west of UTC) and ``daylight``
+ (to 0 if this timezone does not have any daylight saving time rules, or to
+ nonzero if there is a time, past, present or future when daylight saving time
+ applies).
Availability: Unix.