Time in Mexico

Mexico uses four main time zones since February 2015:

In addition, the law dictates that all island territories should fall within the time zone corresponding to their geographic location.

Standard time was first defined in Mexico in 1921, when President Álvaro Obregón decreed two time zones. One time zone designated for 90° W covered the states of Tabasco, Chiapas, Campeche, Yucatán, and Quintana Roo. A second time zone designated for 105° W covered the rest of the country, from Baja California to Veracruz and Oaxaca.

In 1930 three zones were decreed: Hora del Oeste (120° W) for the state of Baja California (norte); Hora del Golfo (90° W) covering the states of Tamaulipas, Veracruz, Oaxaca, Tabasco, Chiapas, Campeche, Yucatán and Quintana Roo; and Hora del Centro (105° W) for the rest of the country.

It was decreed in 1942 that the Hora del Noroeste (105° W) should cover only the states of Baja California Sur, Sonora, Sinaloa, and Nayarit; while the Hora del Centro (90° W) was used for the rest of the country.

The time zone Hora del Sureste (75° W) was created for tourist reasons in 1981, originally covering the states of Campeche, Yucatán, and Quintana Roo. The three states returned one year later to the Hora del Centro (90° W); Quintana Roo, however, returned to the Hora del Sureste (75° W) from October 1997 to August 1998 and then again in February 2015.

First observation of DST was in 1931, but only for the state of Baja California. It used the "Hora del Centro" from April 1 to September 30, and the "Hora del Oeste" the rest of the year. Until 1996, Baja California was the only Mexican state to officially observe DST every year, coinciding with the observance of DST across the border in San Diego, California. In addition to that, the states of Durango, Coahuila, Nuevo Leon and Tamaulipas unofficially observed DST in 1988 as an experiment, starting on the first Sunday in April and ending on the last Sunday in October. These states abandoned DST the following year and did not return to it until DST was adopted nationwide.

Daylight saving time has been observed nationwide in Mexico beginning in 1996. For municipalities located less than 20 km from the US border, such as Ciudad Juarez, and the entire state of Baja California (Norte), it coincides with the longer extended daylight saving period adopted for 2007 in the United States. But in the rest of the country, daylight saving time is observed between 2 a.m. on the first Sunday in April through 2 a.m. on the last Sunday in October. Quintana Roo and Sonora states do not observe DST.

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Wikipedia