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Atlantic Time (AT)

Also known as: Atlantic Standard Time (AST) and Atlantic Daylight Time (ADT)

Time zone map of ADT
Currently observing ADT.
Areas with same time currently (UTC -3).
Currently observing ADT – Atlantic Daylight Time.
Currently has same time zone offset as ADT (UTC -3) but different time zone name.

The term Atlantic Time (AT) is often used to denote the local time in areas observing either Atlantic Daylight Time (ADT) or Atlantic Standard Time (AST).

In other words, in locations observing Daylight Saving Time (DST) during part of the year, Atlantic Time is not static but switches between ADT and AST.

Atlantic Time UTC Offset

See Time Zone Map

What Is Atlantic Time?

Atlantic Time (AT) is an eastern time zone in North America. It is used in the northeast of Canada and the US territories Puerto Rico and the US Virgin Islands.

It is not currently used in mainland United States.

In North America, Atlantic Time shares a border with Eastern Time (ET) in the west.

What Does AT Time Zone Mean?

Unlike other time zone denominations, which have a fixed time, Atlantic Time refers to a geographical area where the time changes twice yearly as Daylight Saving Time (DST) begins and ends. Atlantic Standard Time is UTC-4, while Atlantic Daylight Time is UTC-3.

Most North American time zones have generic terms, including Pacific Time (PT), Mountain Time (MT), Central Time (CT), and Eastern Time (ET).

Converting Atlantic Time to Other US Time Zones

Where and when is Atlantic Time observed?

North America

Canadian provinces using AST in the winter and ADT in the summer

  • Most of Labrador (mainland part of the province of Newfoundland and Labrador)
  • New Brunswick
  • Nova Scotia
  • Prince Edward Island

Areas of Greenland using AST in the winter and ADT in the summer

  • Thule area


Atlantic islands/territories using AST in the winter and ADT in the summer

  • Bermuda

AST all year round

Some locations, such as the ones below don't switch and are in AST all year long.

North America

Canadian provinces using AST all year

  • Quebec - East of 63 West only.


Caribbean countries/territories using AST all year

  • Anguilla
  • Antigua and Barbuda
  • Aruba
  • Barbados
  • British Virgin Islands
  • Caribbean NetherlandsShow

    Bonaire, Sint Eustatius, Saba

  • Curaçao
  • Dominica
  • Dominican Republic
  • Grenada
  • Guadeloupe
  • Martinique
  • Montserrat
  • Puerto Rico
  • Saint Barthélemy
  • Saint Kitts and Nevis
  • Saint Lucia
  • Saint Martin (FR)
  • Saint Vincent and Grenadines
  • Sint Maarten (NL)
  • Trinidad and Tobago
  • Turks and Caicos Islands
  • US Virgin Islands