Atlantic/Bermuda time zone

About Atlantic/Bermuda

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

Its principal location is Bermuda at 32.28° N, 64.77° 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

• Sunday, March 14, 2027: at 2:00 AM clocks go forward 1 hour to 3:00 AM (ADT, UTC−3)
• Sunday, November 7, 2027: at 2:00 AM clocks go back 1 hour to 1:00 AM (AST, UTC−4)
• Sunday, March 12, 2028: at 2:00 AM clocks go forward 1 hour to 3:00 AM (ADT, UTC−3)
• Sunday, November 5, 2028: at 2:00 AM clocks go back 1 hour to 1:00 AM (AST, UTC−4)
• Sunday, March 11, 2029: at 2:00 AM clocks go forward 1 hour to 3:00 AM (ADT, UTC−3)
• Sunday, November 4, 2029: at 2:00 AM clocks go back 1 hour to 1:00 AM (AST, UTC−4)
• Sunday, March 10, 2030: at 2:00 AM clocks go forward 1 hour to 3:00 AM (ADT, UTC−3)
• Sunday, November 3, 2030: at 2:00 AM clocks go back 1 hour to 1:00 AM (AST, UTC−4)
• Sunday, March 9, 2031: at 2:00 AM clocks go forward 1 hour to 3:00 AM (ADT, UTC−3)
• Sunday, November 2, 2031: at 2:00 AM clocks go back 1 hour to 1:00 AM (AST, UTC−4)
• Sunday, March 14, 2032: at 2:00 AM clocks go forward 1 hour to 3:00 AM (ADT, UTC−3)

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

History of Atlantic/Bermuda since 1970

The record starts with local mean time (UTC−4:19), which ended on January 1, 1890. The first daylight saving time in the record is in 1917.

Before 1970

27 offset changes before 1970 in the record; the first 12 and the last 12:

• Friday, April 6, 1917: UTC−4:19 → UTC−3:19 (BST), daylight saving time
• Monday, October 1, 1917: UTC−3:19 → UTC−4:19 (BMT)
• Sunday, April 14, 1918: UTC−4:19 → UTC−3:19 (BST), daylight saving time
• Monday, September 16, 1918: UTC−3:19 → UTC−4:19 (BMT)
• Wednesday, January 1, 1930: UTC−4:19 → UTC−4 (AST)
• Sunday, January 11, 1942: UTC−4 → UTC−3 (ADT), daylight saving time
• Sunday, October 18, 1942: UTC−3 → UTC−4 (AST)
• Sunday, March 21, 1943: UTC−4 → UTC−3 (ADT), daylight saving time
• Sunday, October 31, 1943: UTC−3 → UTC−4 (AST)
• Sunday, March 12, 1944: UTC−4 → UTC−3 (ADT), daylight saving time
• Sunday, November 5, 1944: UTC−3 → UTC−4 (AST)
• Sunday, March 11, 1945: UTC−4 → UTC−3 (ADT), daylight saving time
• Sunday, May 23, 1948: UTC−4 → UTC−3 (ADT), daylight saving time
• Sunday, September 5, 1948: UTC−3 → UTC−4 (AST)
• Sunday, May 22, 1949: UTC−4 → UTC−3 (ADT), daylight saving time
• Sunday, September 4, 1949: UTC−3 → UTC−4 (AST)
• Sunday, May 28, 1950: UTC−4 → UTC−3 (ADT), daylight saving time
• Sunday, September 3, 1950: UTC−3 → UTC−4 (AST)
• Sunday, May 27, 1951: UTC−4 → UTC−3 (ADT), daylight saving time
• Sunday, September 2, 1951: UTC−3 → UTC−4 (AST)
• Sunday, May 25, 1952: UTC−4 → UTC−3 (ADT), daylight saving time
• Sunday, September 7, 1952: UTC−3 → UTC−4 (AST)
• Sunday, May 27, 1956: UTC−4 → UTC−3 (ADT), daylight saving time
• Sunday, October 28, 1956: UTC−3 → UTC−4 (AST)

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, America/Thule.

Places on Atlantic/Bermuda

• HamiltonBM

Convert Bermuda time

Using Atlantic/Bermuda 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: 'Atlantic/Bermuda' })

# Python 3.9+
from zoneinfo import ZoneInfo
from datetime import datetime
datetime.now(ZoneInfo('Atlantic/Bermuda'))

// Java
java.time.ZonedDateTime.now(java.time.ZoneId.of("Atlantic/Bermuda"))

// Go
loc, _ := time.LoadLocation("Atlantic/Bermuda")
time.Now().In(loc)

-- PostgreSQL
SELECT now() AT TIME ZONE 'Atlantic/Bermuda';

# Shell
TZ='Atlantic/Bermuda' 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.

Related

• Time zones of the world
• AST time
• ADT time
• UTC−4 time
• Time in Hamilton
• Daylight saving time