areas advanced their clocks by an hour, so that they became part of the UTC−04:00 time zone. However, in a non-binding referendum held on 31 October 2010, a slight majority of Acre voters voted in favour of returning the state to UTC−05:00. On 30 October 2013, Brazilian President Dilma Rousseff enacted Law 12876, establishing that the time zone switch would occur on Sunday, 10 November 2013. Since then, the state of Acre and the southwestern part of the state of Amazonas are again 5 hours behind UTC. Unofficial observance Unofficially, 32 municipalities in eastern Mato Grosso, located in the Araguaia valley, observe UTC−03:00, Brasília time. This practice started in Barra do Garças in 1998. Banks and government services still observe the legal time in these locations (UTC–04:00). Unofficially, the municipality of Bataguassu in eastern Mato Grosso do Sul also observes UTC−03:00, Brasília time. Daylight saving time Brazil observed daylight saving time (DST; , "summer time") in the years of 1931–1933, 1949–1953, 1963–1968 and 1985–2019. Initially it applied to the whole country, but from 1988 it applied only to part of the country, usually the southern regions, where DST is more useful due to a larger seasonal variation in daylight duration. It typically lasted from October or November to February or March. The most recent DST rule specified advancing the time by one hour during the period from 00:00 on the first Sunday in November to 00:00 on the third Sunday in February (postponed by one week if the latter fell on carnival), applicable only to the South, Southeast and Central-West regions, which comprise about 64% of the Brazilian population. During DST, Brasília time moved from UTC−03:00 to UTC−02:00; the other states that did not follow DST observed a change of the offset to Brasília time. Brazil abolished DST in 2019. IANA time zone database The IANA time zone database contains 16 zones for Brazil. Columns marked with * are from the file zone.tab of the database. See also Date and time notation in Brazil List of time zones Notes References External links Time Service Division of the National Observatory of Brazil Legal time in Brazil Time in South America