Buenos Aires time zone history
Daylight saving time was used in 12 years since 1970, last in 2009; under the current rules the clocks no longer change. On standard time, clocks in Buenos Aires run 54 minutes ahead of local mean solar time.
UTC−3
Standard time is UTC−3 all year under the current rules.
Summer time in 12 of 57 years since 1970
Before 1970
Standard time changes
| Date | Change | New standard time | Clock label |
|---|---|---|---|
| Before 1970 | |||
| October 31, 1894 | Local mean time (UTC−3:53:48) replaced | UTC−4:16:48 | CMT |
| May 1, 1920 | Standard time forward 17 minutes | UTC−4 | numeric only |
| October 5, 1969 | Standard time forward 1 hour | UTC−3 | numeric only |
| Since 1970 | |||
| October 3, 1999 | Summer offset kept as standard time; clocks did not move | UTC−4 | numeric only |
| March 3, 2000 | Summer offset kept as standard time; clocks did not move | UTC−3 | numeric only |
Daylight saving periods
| Years | Clocks go forward | Clocks go back | Shift and labels |
|---|---|---|---|
| Before 1970 | |||
| 1930 | December 1 | not that year | 1 hour |
| 1931 | October 15 | April 1 | 1 hour |
| 1932–1939 | 1 November, 00:00 | 1 March, 00:00 | 1 hour |
| 1940 | July 1 | March 1 | 1 hour |
| 1941 | October 15 | June 15 | 1 hour |
| 1943 | October 15 | August 1 | 1 hour |
| 1946 | October 1 | March 1 | 1 hour |
| 1963 | December 15 | October 1 | 1 hour |
| 1964–1966 | 15 October, 00:00 | 1 March, 00:00 | 1 hour |
| 1967–1968 | first Sunday in October, 00:00 | first Sunday in April, 00:00 | 1 hour |
| 1969 | not that year | April 6 | 1 hour |
| Since 1970 | |||
| 1974 | January 23 | May 1 | 1 hour |
| 1988 | December 1 | not that year | 1 hour |
| 1989–1992 | third Sunday in October, 00:00 | first Sunday in March, 00:00 | 1 hour |
| 1993 | not that year | March 7 | 1 hour |
| 2007 | December 30 | not that year | 1 hour |
| 2008 | October 19 | March 16 | 1 hour |
| 2009 | not that year | March 15 | 1 hour |
Also on UTC−3
Uruguay, Cordoba (Argentina), San Luis (Argentina), Catamarca (Argentina), Mendoza (Argentina), La Rioja (Argentina), San Juan (Argentina), Paraguay, Tucumán (Argentina) and Salta (Argentina) (nearest first; 19 more on the list of offsets).
Clocks next door since 1970
- Uruguay (207 km): same time except 2,711 days in 1970, 1972, 1974–1980, 1987–1991, 1993 and 2004–2015.
- Cordoba (642 km): same time except 231 days in 1991.
- San Luis (742 km): same time except 1,398 days in 1990–1993, 2004, 2008 and 2009.
- Catamarca (973 km): same time except 397 days in 1991, 2004, 2008 and 2009.
- Mendoza (977 km): same time except 1,221 days in 1990–1992, 2004, 2008 and 2009.
- Santiago (Chile) (1,132 km): usually 1 hour behind; different on 9,361 days in 1970–2026.