The time module defines timezone, altzone, tzname and daylight constants that store information about system timezone.  This information is derived  from the timezone rules that are in effect at the module loading time, but may be incorrect for the times in the past.  The documentation should warn the user about this and recommend using the tm_zone and tm_gmtoff attributes in the result of time.localtime() to obtain timezone information.  See #22799 and msg148208.