Cook Islands time zone history
Rarotonga kept local mean time (UTC−10:39:04) until 1952, tied for the latest switch among the 298 zones with local mean time in the record. Its seasonal clock changes since 1970 include moves of 30 minutes, not the usual hour. Since 1970 it has also used UTC−10:30, an offset that is not a whole number of hours.
UTC−10
Standard time is UTC−10 all year under the current rules.
Summer time in 14 of 57 years since 1970
Before 1970
Standard time changes
| Date | Change | New standard time | Clock label |
|---|---|---|---|
| Before 1970 | |||
| December 26, 1899 | Standard time back 24 hours | UTC−10:39:04 | LMT |
| October 16, 1952 | Local mean time (UTC−10:39:04) replaced | UTC−10:30 | numeric only |
| Since 1970 | |||
| November 12, 1978 | Standard time forward 30 minutes | UTC−10 | numeric only |
Daylight saving periods
| Years | Clocks go forward | Clocks go back | Shift and labels |
|---|---|---|---|
| 1979–1990 | last Sunday in October, 00:00 | first Sunday in March, 00:00 | 30 minutes |
| 1991 | not that year | March 3 | 30 minutes |
Also on UTC−10
Tahiti (French Polynesia), Honolulu (United States) and Adak (United States).
Clocks next door since 1970
- Niue (1,088 km): usually 1 hour behind; different on 4,875 days in 1970–1991.
- Tahiti (French Polynesia) (1,146 km): same time except 4,875 days in 1970–1991.
- American Samoa (1,392 km): usually 1 hour behind; different on 4,875 days in 1970–1991.
- Samoa (1,511 km): usually 1 hour behind; different on 10,641 days in 1970–1991 and 2010–2026; 23 hours ahead today.
- Tonga (1,600 km): usually 23 hours ahead; different on 5,277 days in 1970–1991, 1999–2002, 2016 and 2017.
How it compares
Daylight saving time was used in 14 years since 1970, last in 1991; under the current rules the clocks no longer change.
On standard time, clocks in Rarotonga run 39 minutes ahead of local mean solar time.