Technical Specifications & Standards
Official chronometric properties, ISO standards, and international database registry identifiers for Hawaii-Aleutian Daylight Time:
Daylight Saving Time (DST) Transitions
⬆️ Spring Forward (Clocks Advance)
Clocks advance 1 hour from HAST on the second Sunday in March at 02:00
⬇️ Fall Back (Clocks Return)
Clocks return 1 hour to HAST on the first Sunday in November at 02:00
Observing Jurisdictions & Subdivisions
1 Sovereign NationsSovereign nations, administrative subdivisions, and regional territories officially operating under HADT:
Regional Subdivisions & Territory Details
Financial Markets & Trading Hours
Facilitates Bering Sea commercial king crab and pollock fisheries and transpacific air cargo fueling logistics.
Local Hours: 09:00 - 17:00 HADT
UTC Window: 18:00 - 02:00 UTC
Major Cities in HADT
Primary metropolitan centers and financial hubs observing this time zone:
Adoption History & Astronomical Facts
Year Established: 1983
When Alaska consolidated four time zones into two in 1983, the western Aleutian Islands were designated as observing Hawaii-Aleutian time with daylight saving, shifting to UTC-9 in summer.
Adak Island is the southernmost town in Alaska and the westernmost municipality in the United States, observing HADT in summer.
Frequently Asked Questions about HADT
What is HADT?
HADT stands for Hawaii-Aleutian Daylight Time, which is UTC-9.
Does Hawaii use HADT?
No. Hawaii does not observe daylight saving time; only Alaska's western Aleutian Islands observe HADT.
What is the standard time counterpart to HADT?
Hawaii-Aleutian Standard Time (HAST, UTC-10) is the winter counterpart.