ADT time now (Atlantic Daylight Time)

What ADT means

ADT stands for Atlantic Daylight Time, UTC−3. It is used in the Canadian Maritimes, Bermuda and Thule in Greenland.

It is a summer time: the daylight saving form of AST (UTC−4), one hour ahead. In Halifax it applies from March to October/November: from the second Sunday of March at 2:00 AM to the first Sunday of November at 2:00 AM.

Where and when ADT is used

6 zones use it for part of the year only, switching back to standard time in the other months. Computed from tzdata under the current rules.

How long ADT has been used

In the tzdata record, Halifax has used ADT since 1916, Sydney has used ADT since 1918 and Moncton has used ADT since 1918.

ADT in the past

Zones whose tzdata history shows ADT before 2025 but that no longer use it:

• America/Barbados (Bridgetown): 1942–1980
• America/Martinique (Fort-de-France): 1980

ADT converted to other zones

Every column is a fixed offset, so this table is valid on any date. Remember that the regions behind some columns switch to summer time (EST to EDT, CET to CEST, GMT to BST); the clock in those cities is then an hour later than the column.

Related zones and conversions

• AST time
• America/Halifax time zone
• UTC−3 time
• Time zones of the world
• Daylight saving time
• Time zone converter