Texas time zones

49 CFR 71.7(e) follows the east line of Hudspeth County from the New Mexico border to Mexico. El Paso County, west of Hudspeth, and Hudspeth itself are Mountain Time. Every other Texas county, including Culberson County just east of that line, is Central Time.

Both zones observe daylight saving time. El Paso therefore changes clocks with Denver, not with Dallas. The two mountain counties are the entire Texas exception; the sample did not find a third.