The abbreviations for the time zone for standard and daylight savings time
#include <time.h> char *tzname;
This global variable holds the standard abbreviations for the time zone and the time zone when daylight saving time is in effect. Whenever you call a time function, tzset() is called to set the values in the array, based on the current time zone.
POSIX 1003.1 XSI
daylight, timezone, tzset()
“Setting the time zone” in the Configuring Your Environment chapter of the Neutrino User's Guide