In most of Mexico daylight saving time begins at 2:00 a.m. local time on the first Sunday in April. On the last Sunday in October areas on daylight saving time fall back to Standard Time at 2:00 a.m. local time. Central Standard Time (CST) becomes Central Daylight Time (CDT), and so forth. The state of Sonora does not observe daylight saving time. During daylight saving time turn your clocks ahead one hour. At the end of daylight saving time turn your clocks back one hour.

NEW! In 2010 ten Mexico municipalities which share a border with the United States will begin daylight saving time three weeks earlier on the second Sunday in March and end on the first Sunday in November. Previously all of Mexico, with the exception of the state of Sonora which does not observe daylight saving time, began and ended daylight saving time at the same time. The Congress of Mexico passed legislation in December 2009 which allowed these ten border cities to adopt a daylight saving time pattern consistent with the United States. The municipalities which are now permitted by law to observe daylight saving time consistent with the United States are:

City, State
Acuna, Coahuila
Anahuac, Nuevo Leon
Juarez, Chihuahua
Matamoros, Tamaulipas
Mexicali, Baja California
Nuevo Laredo, Tamaulipas
Ojinaga, Chihuahua
Piedras Negras, Coahuila
Reynosa, Tamaulipas
Tijuana, Baja California

The observation of daylight saving time for these ten municipalities will begin at 2:00 a.m. local time on the second Sunday in March. On the first Sunday in November these areas will return to Standard Time at 2:00 a.m. local time.

This change in daylight saving time observance was requested by local governments and political leaders to help facilitate commerce with the United States. Industries such as transportation and banking were especially affected by the differences in daylight saving time. In some cases businesses had to to open an hour early than usual to conduct business with US companies during the 3 weeks in March when the two countries were on different times.

Some smaller towns and villages surrounding these ten municipalities may unofficially follow the extended daylight saving time pattern.

See more here>>http://www.timetemperature.com/tzmx/mexico_dst.shtml