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America/Thule time zone

9:42AMAST

ASTUTC−4+1 h vs New York (you)

About America/Thule

America/Thule is the IANA time zone for Thule/Pituffik in Greenland. It currently keeps Atlantic Standard Time (AST, UTC−4) in winter and Atlantic Daylight Time (ADT, UTC−3) in summer.

Its principal location is Thule at 76.57° N, 68.78° W.

Abbreviations in use: AST, ADT. Offset page: UTC−4.

Rule for future years (POSIX TZ string)

AST4ADT,M3.2.0,M11.1.0

The standard time is called AST and is UTC−4. POSIX writes the offset with the opposite sign (west of Greenwich is positive), which is why the string says "4". Daylight saving time is called ADT and is UTC−3. 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/Thule since 1970

The record starts with local mean time (UTC−4:35), which ended on July 28, 1916. The first daylight saving time in the record is in 1991.

YearsClocksAbbreviations
1970–1990UTC−4 all yearAST
1991 onwardUTC−4 in winter, UTC−3 in summerAST, ADT

Before 1970

1 offset change before 1970 in the record:

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

Other zones that keep exactly the same time under the current rules (but have a different history): America/Glace_Bay, America/Goose_Bay, America/Halifax, America/Moncton, Atlantic/Bermuda.

Convert Thule time

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

Using America/Thule 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/Thule' })

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

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

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

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

# Shell
TZ='America/Thule' 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/Thule?
UTC−4 in winter and UTC−3 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/Thule 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.
Which countries use America/Thule?
Greenland, according to zone1970.tab in tzdata.

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