Adak time zone history
On standard time, clocks at Adak run 1 hour 47 minutes ahead of local mean solar time, the seventh-largest gap of the 233 zones whose clocks run ahead of the sun. Local mean time, UTC−11:46:38, ended in 1900.
UTC−10
Standard time is UTC−10 (HDT/HST); clocks go forward to UTC−9 on the second Sunday in March and back on the first Sunday in November.
Summer time in every year since 1970
Before 1970
Standard time changes
| Date | Change | New standard time | Clock label |
|---|---|---|---|
| Before 1970 | |||
| October 19, 1867 | Standard time back 24 hours | UTC−11:46:38 | LMT |
| August 20, 1900 | Local mean time (UTC−11:46:38) replaced | UTC−11 | NST |
| Since 1970 | |||
| October 30, 1983 | Summer offset kept as standard time; clocks did not move | UTC−10 | AHST |
Daylight saving periods
| Years | Clocks go forward | Clocks go back | Shift and labels |
|---|---|---|---|
| Before 1970 | |||
| 1942 | February 9 | not that year | 1 hour, NST to NWT |
| 1945 | not that year | September 30 | 1 hour |
| 1969–1973 | last Sunday in April, 02:00 | last Sunday in October, 02:00 | 1 hour, BST to BDT |
| Since 1970 | |||
| 1974 | January 6 | October 27 | 1 hour, BST to BDT |
| 1975 | February 23 | October 26 | 1 hour, BST to BDT |
| 1976–1982 | last Sunday in April, 02:00 | last Sunday in October, 02:00 | 1 hour, BST to BDT |
| 1983 | April 24 | not that year | 1 hour, BST to BDT |
| 1984–1986 | last Sunday in April, 02:00 | last Sunday in October, 02:00 | 1 hour, HST to HDT |
| 1987–2006 | first Sunday in April, 02:00 | last Sunday in October, 02:00 | 1 hour, HST to HDT |
| 2007–2037 | second Sunday in March, 02:00 | first Sunday in November, 02:00 | 1 hour, HST to HDT |
Clock changes in 2026, 2027 and 2028
The clocks go forward 1 hour (HST to HDT) on March 8, 2026, March 14, 2027 and March 12, 2028 at 02:00 and back 1 hour (HDT to HST) on November 1, 2026, November 7, 2027 and November 5, 2028 at 02:00, local time.
Also on UTC−10
Honolulu (United States), Tahiti (French Polynesia) and Cook Islands.
Clocks next door since 1970
- Anadyr (Russia) (1,470 km): usually 22 hours ahead; different on 10,123 days in 1970–2026.
- Nome (1,545 km): usually 1 hour ahead; different on 5,054 days in 1970–2026.
- Kamchatka (Russia) (1,670 km): usually 22 hours ahead; different on 7,901 days in 1970–2026.
- Anchorage (1,920 km): usually 1 hour ahead; different on 5 days in 1970–2026.
- Magadan (Russia) (2,182 km): usually 21 hours ahead; different on 7,262 days in 1970–2026.