Most of Texas is in the Central Time Zone with the exception being the two westernmost counties.
Northwestern Culberson County near Guadalupe Mountains National Park unofficially observes Mountain Time Zone.
The 2 zones for Texas as given by zone.tab of the IANA time zone database. Columns marked * are from the zone.tab.
|c.c.*||coordinates*||TZ*||comments*||UTC offset||UTC offset DST||Note|
|US||+415100−0873900||America/Chicago||Central (most areas)||−06:00||−05:00|
|US||+394421−1045903||America/Denver||Mountain (most areas)||−07:00||−06:00|
The "Panhandle and Plains" section of Texas is now in the Central Time Zone, but had a two-year period of being in the Mountain Time Zone between 1919 and 1921.