Time zone · Americas
HST
Hawaii-Aleutian Standard Time
Hawaii-Aleutian Time stretches across remote volcanic islands in the Pacific, blending Hawaiian island life with the rugged, windswept Aleutian chain off Alaska. It's a region where the clock itself seems split—Daylight Saving Time runs on Adak but not in Honolulu—so the two are an hour apart from March to November.
Wednesday, October 14, 2026
Current offset
UTC-10:00
Standard · HST
Daylight saving
Not active
Year-round standard time
IANA zones
2
1 observe DST, 1 doesn't
DST offset
UTC-09:00
HDT · +1h
About HST
Standard time, with a summer shift.
Hawaii-Aleutian Time stretches across remote volcanic islands in the Pacific, blending Hawaiian island life with the rugged, windswept Aleutian chain off Alaska. It's a region where the clock itself seems split—Daylight Saving Time runs on Adak but not in Honolulu—so the two are an hour apart from March to November.
IANA zones · the technical identifiers
The 2 zones that resolve to HST.
For software, always store the IANA identifier — never the abbreviation alone. The database keeps these zones distinct because their rules can, and historically did, diverge.
Where HST is used
One country.
Same offset · UTC-10:00
Other zones at UTC-10:00 right now.
These named zones share HST's offset today. When daylight saving rules differ, they drift apart for part of the year.
Convert
HST to the world's clocks.
Frequently asked questions
Common questions about HST, daylight saving, and how to handle it in software. Can't find what you need? Email [email protected].
- Why does only part of Hawaii-Aleutian Time observe Daylight Saving Time?
- Adak, in the Aleutian Islands of Alaska, follows DST along with most of the continental US, while Honolulu in Hawaii opts out. This split means the two zones that share the same base code are an hour apart for almost eight months of the year, from March to November.
- Is Hawaii-Aleutian Standard Time the same as Hawaii Standard Time?
- Mostly, yes—Honolulu operates on HST year-round, which is UTC-10:00. However, during the DST months, Adak shifts to Hawaii-Aleutian Daylight Time (HDT), which is UTC-09:00, creating a one-hour difference between the two areas.
- What is the westernmost time zone in the United States?
- Among the 50 states, Hawaii-Aleutian Time is the westernmost zone. Adak, in the Aleutian Islands, is the westernmost US city; it uses HDT (UTC-09:00) from March to November and HST (UTC-10:00) otherwise. US territories such as American Samoa (UTC-11:00) are further behind.
- How does living in Hawaii-Aleutian Time affect daily life?
- Honolulu stays on UTC-10:00 while the mainland observes daylight saving time, so it is 2 hours behind Los Angeles in winter and 3 hours behind in summer. Adak changes its clocks with the mainland, so its gap stays the same.
- Why is Hawaii-Aleutian Daylight Time (HDT) one of the rarest time zone abbreviations?
- HDT is only used in a tiny portion of the Aleutian Islands, making it one of the least commonly referenced time zone codes.
- How do people on Adak adjust when DST ends?
- On the first Sunday in November, clocks on Adak fall back from HDT (UTC-09:00) to HST (UTC-10:00), aligning with Honolulu for the winter months until DST begins again on the second Sunday in March.
- Is there a big difference in sunrise and sunset times across this region?
- Yes. Adak lies about 30 degrees of latitude further north than Honolulu, so its summer days are much longer (over 16 hours at the June solstice, against about 13.5 hours in Honolulu) and its winter days much shorter.
Source: IANA tzdb2026d · Reviewed
Free · Developer API
This time zone, as JSON.
Its defining offset, DST status and member counts, from one endpoint.
Also in the API: time zones by coordinates, conversions that flag daylight saving gaps, and abbreviations decoded.
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