Time in Mexico

History

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.

Daylight saving time

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.

As the United States starts DST on the second Sunday in March and ends it on the first Sunday in November, Mexico's time zones are out of synchronization with American and Canadian time zones for two periods each year. The first is the three or four weeks between the second Sunday in March and the first Sunday in April. The second is the single week between the last Sunday in October and the first Sunday in November. During these periods, clocks in Mexico City match those in Denver rather than those in Chicago. The Mexican Stock Exchange changes its hours during these periods in order to maintain synchronization with the U.S. markets. Conversely, television schedules are not changed for these situations, meaning Mexican television networks which are carried directly by American cable and satellite services have their programming aired an hour ahead or behind in the United States during these interregnums.

In 1998 the state of Chihuahua moved from Central time to Mountain time. This is likely because Ciudad Juárez is directly across the border from El Paso, Texas, which is on Mountain Time. Later, in 2001, Mexico experimented with a shorter daylight saving period from the first Sunday in May till the last Sunday in September, returning to the previous seven month schedule in 2002. When the United States extended their DST period in 2007, the mexican congress refused to do the same for Mexico. Two years later, the population of the northern border cities complained about the time difference between those cities and their US counterparts and their government requested the DST extension again. For the second time, congress refused to adopt it nationwide. As a result, only the areas within 20 km of the United States border, as well as all of Baja California, began observing DST on the US schedule in 2010, while the rest of the country retained the pre-2007 United States DST schedule. A new bill was proposed in September 2015 for the rest of the country to also observe DST on the extended 2007 US schedule, thus eliminating the distinction between the border cities and the rest of Mexico. Congress refused to approve the change for the third time in a 10-year period, discarding the bill on June 29, 2016.

Daylight saving time is observed in all parts of the country except for the states of Quintana Roo, and Sonora, which decided to remain on standard time beginning in 1999. This is to coincide with the non-observation in Arizona, with which Sonora shares its northern border. The island territories do not currently observe daylight time either. During non-DST period, Mexico uses 4 different time zones.

IANA time zone database

Data for Mexico from zone.tab in the IANA time zone database. Columns marked with * are the columns from zone.tab itself.

On 2010-01-06 a zone America/Ensenada named for Ensenada, Baja California was scheduled for inclusion with the comment "Split off Mexican cities (near US border) that are to follow US rules starting in 2010. Tijuana splits into Tijuana and Ensenada".