Rio Branco time zone history
On standard time, clocks at Rio Branco run 29 minutes behind local mean solar time, the sixth-largest gap of the 79 zones whose clocks run behind the sun. The Rio Branco zone has changed its standard time twice since 1970, tied for the most among the 16 zones in Brazil. The latest change of standard time came on November 10, 2013, from UTC−4 to UTC−5.
UTC−5
Standard time is UTC−5 all year under the current rules.
Summer time in 4 of 57 years since 1970
Before 1970
Standard time changes
| Date | Change | New standard time | Clock label |
|---|---|---|---|
| Before 1970 | |||
| January 1, 1914 | Local mean time (UTC−4:31:12) replaced | UTC−5 | numeric only |
| Since 1970 | |||
| June 24, 2008 | Standard time forward 1 hour | UTC−4 | numeric only |
| November 10, 2013 | Standard time back 1 hour | UTC−5 | numeric only |
Daylight saving periods
| Years | Clocks go forward | Clocks go back | Shift and labels |
|---|---|---|---|
| 1931 | October 3 | not that year | 1 hour |
| 1932 | October 3 | April 1 | 1 hour |
| 1933 | not that year | April 1 | 1 hour |
| 1949 | December 1 | not that year | 1 hour |
| 1950 | December 1 | April 16 | 1 hour |
| 1951–1952 | 1 December, 00:00 | 1 April, 00:00 | 1 hour |
| 1953 | not that year | March 1 | 1 hour |
| 1963 | December 9 | not that year | 1 hour |
| 1964 | not that year | March 1 | 1 hour |
| 1965 | January 31, December 1 | April 1 | 1 hour |
| 1966–1967 | 1 November, 00:00 | 1 March, 01:00 | 1 hour |
| 1968 | not that year | March 1 | 1 hour |
Since 1970: the periods shared by 4 of 16 zones, listed on the Brazil page.
Also on UTC−5
Eirunepé (Brazil), Peru, Guayaquil (Ecuador), Colombia, Panama, Haiti, Jamaica, Turks and Caicos Islands, Cuba and Cancún (Mexico) (nearest first; 13 more on the list of offsets).
Clocks next door since 1970
- Eirunepé (432 km): same time except 126 days in 1993 and 1994.
- Porto Velho (448 km): usually 1 hour ahead; different on 1,965 days in 1985–1988 and 2008–2013.
- Bolivia (727 km): usually 1 hour ahead; different on 2,315 days in 1985–1988 and 2008–2013.
- Peru (1,036 km): same time except 2,441 days in 1985–1988, 1990, 1994 and 2008–2013.
- Manaus (1,147 km): usually 1 hour ahead; different on 2,091 days in 1985–1988, 1993, 1994 and 2008–2013.
How it compares
Daylight saving time was used in 4 years since 1970, last in 1988; under the current rules the clocks no longer change.
Rio Branco kept local mean time (UTC−4:31:12) until 1914, tied second-latest switch among the 23 zones on UTC−5 standard time with local mean time in the record.