The number of seconds by which the local time zone is earlier than UTC
#include <time.h> long int timezone;
This global variable holds the number of seconds by which the local time zone is earlier than Coordinated Universal Time (UTC) (formerly known as Greenwich Mean Time). Whenever you call a time function, tzset() is called to set the variable, based on the current time zone.
"Setting the time zone" in the Configuring Your Environment chapter of the Neutrino User's Guide