Definitions for TIME ZONE
Random House Webster's College Dictionary
one of the 24 regions or divisions of the globe approximately coinciding with meridians at successive hours from the observatory at Greenwich, England.
Origin of time zone:
any of the 24 regions of the globe (loosely divided by longitude) throughout which the same standard time is used
Kernerman English Learner's Dictionary
time zone(noun)ˈtaɪmˌteɪ bəl
one of the areas the world is divided into according to time
two cities that are in different time zones
A range of longitudes where a common standard time is used.