IANA tz database · zone identifier

America/Adak

The IANA tz database identifier for Hawaii-Aleutian Standard Time in United States. Store this string — not the abbreviation, not the offset — and your timestamps stay correct forever.

UTC-09:00Abbreviation HDTObserves daylight saving
Time in America/Adak☀ Daylight
13:58:03
Wednesday, July 15, 2026
Offset
UTC-09:00
Abbreviation
HDT
DST
Active

Current offset

UTC-09:00

standard UTC-10:00 · daylight UTC-09:00

Abbreviation

HDT

the daylight-saving form

DST behaviour

Observes

changes clocks twice a year

Country

🇺🇸 United States

ISO 3166: US · view country page →

Using this identifier

The string to put in your code.

America/Adak is the identifier to use in code and config for this region. Every modern language, database, and OS resolves it through the same tz database, so the examples here behave identically everywhere.

Avoid storing HDT or -09:00 — abbreviations are ambiguous and fixed offsets can't follow rule changes.

// format a date in this zone
new Intl.DateTimeFormat('en-US', {
timeZone: 'America/Adak',
dateStyle: 'full', timeStyle: 'long'
}).format(new Date());

Offset & DST behaviour

Two offsets,
every year.

America/Adak alternates between HST (UTC-10:00) and HDT (UTC-09:00). Right now it is on HDT; clocks fall back on 1 November 2026.

The year at a glance

HST · UTC-10:00HDT · UTC-09:00HST · UTC-10:008 Mar · +1h1 Nov · −1h Jan 2026 Dec

Technical record

The database entry, in full.

source: IANA tz database

IdentifierAmerica/Adak
ISO country codeUS🇺🇸 United States
Reference coordinates51.88°N, 176.66°Wtz database reference point
Standard offsetUTC-10:00abbreviation HST
Daylight offsetUTC-09:00abbreviation HDT

Where it applies

One of United States's 29 zones.

🇺🇸
United States

340M people, 29 time zones — this identifier covers one of them.

Country page →

Related identifiers

Nearby in the database.

Same zone group · Hawaii-Aleutian Standard Time

other identifiers keeping HST

Same offset · UTC-09:00

other zones keeping this offset right now

Frequently asked questions

Answers specific to this identifier — generated from the database record. Can't find what you need? Email [email protected].

What UTC offset is America/Adak?
America/Adak is currently UTC-09:00 (HDT). It alternates between UTC-10:00 in winter and UTC-09:00 in summer.
Does America/Adak observe daylight saving time?
Yes. Clocks fall back at the next transition on 1 November 2026, as they do twice every year.
Which country uses America/Adak?
United States. It is one of 29 IANA zones covering the country.
Is America/Adak the same as HST?
America/Adak is one of the IANA zones that keeps Hawaii-Aleutian Standard Time (HST). Use America/Adak in software — HST is a human-friendly label, not a valid identifier.

Free · Developer API

This zone, as JSON.

Everything on this page — offset, abbreviation, DST rules, coordinates — from one endpoint, always current with the latest tzdb release.

GET /v1/timezones Live

countries, cities, convert, DST transitions coming next.

Get your free API key →
// this identifier, resolved live
GET /v1/timezones?iana=America/Adak
{
"iana": "America/Adak",
"utc_offset": "-09:00",
"abbreviation": "HDT",
"observes_dst": true,
"country": "US"
}