Menu

America/Adak time zone

3:43AMHST

HSTUTC−10−5 h vs New York (you)

About America/Adak

America/Adak is the IANA time zone for Alaska: western Aleutians in United States. It currently keeps Hawaii Time (HST, UTC−10) in winter and Hawaii-Aleutian Daylight Time (HDT, UTC−9) in summer.

Its principal location is Adak at 51.88° N, 176.66° W.

Abbreviations in use: HST, HDT. Offset page: UTC−10.

Rule for future years (POSIX TZ string)

HST10HDT,M3.2.0,M11.1.0

The standard time is called HST and is UTC−10. POSIX writes the offset with the opposite sign (west of Greenwich is positive), which is why the string says "10". Daylight saving time is called HDT and is UTC−9. It starts on the second Sunday of March at 02:00 and ends on the first Sunday of November at 02:00, local time. Software that has no full tzdata copy, such as many embedded devices, can use this string directly as the TZ environment variable.

Upcoming transitions

Computed from tzdata 2026f; local times are read on the clock just before each change.

History of America/Adak since 1970

The record starts with local mean time (UTC+12:13), which ended on October 19, 1867. The first daylight saving time in the record is in 1942.

YearsClocksAbbreviations
1970–1973UTC−11 in winter, UTC−10 in summerBST, BDT
1974mostly UTC−10; also UTC−11 for part of the yearBST, BDT
1975–1982UTC−11 in winter, UTC−10 in summerBST, BDT
1983UTC−11 until April 24, then UTC−10BST, BDT, AHST, HST
1984 onwardUTC−10 in winter, UTC−9 in summerHST, HDT

Before 1970

6 offset changes before 1970 in the record:

Changes of the winter (standard) offset: Sunday, April 24, 1983, UTC−11 → UTC−10.

tzdata commits to accuracy from 1970 for every zone (zone1970.tab); earlier entries are historical research and may be incomplete.

Aliases and zones with the same clock

These older or country-specific IDs are links to America/Adak in tzdata. Their pages redirect here: America/Atka, US/Aleutian.

Convert Adak time

Tip: Alt+↑/↓ steps the time by 15 minutes (Shift: one hour). The link keeps the date, time and direction.

Using America/Adak in code

Every major platform reads the same IANA ID. Store instants in UTC and convert with the ID at display time; never store a fixed offset for a place that has daylight saving time.

// JavaScript
new Date().toLocaleString('en-US', { timeZone: 'America/Adak' })

# Python 3.9+
from zoneinfo import ZoneInfo
from datetime import datetime
datetime.now(ZoneInfo('America/Adak'))

// Java
java.time.ZonedDateTime.now(java.time.ZoneId.of("America/Adak"))

// Go
loc, _ := time.LoadLocation("America/Adak")
time.Now().In(loc)

-- PostgreSQL
SELECT now() AT TIME ZONE 'America/Adak';

# Shell
TZ='America/Adak' date

Platforms ship their own copy of tzdata and update it on their own schedule. After a rule change, outputs can differ until the platform updates; this page uses tzdata 2026f.

Questions

What is the UTC offset of America/Adak?
UTC−10 in winter and UTC−9 in summer (daylight saving time from the second Sunday of March at 2:00 AM to the first Sunday of November at 2:00 AM).
Does America/Adak observe daylight saving time?
Yes: clocks move one hour forward on the second Sunday of March at 2:00 AM and back on the first Sunday of November at 2:00 AM.
Is America/Atka the same as America/Adak?
Yes. America/Atka and US/Aleutian are a link (alias) to America/Adak in tzdata and give the same time since 1970. They remain valid IDs.
Which countries use America/Adak?
United States, according to zone1970.tab in tzdata.

Related