Atlantic Time (AT)

Atlantic Time (AT) is a time zone observed in parts of eastern Canada, the Caribbean, and some areas of South America. It operates on Atlantic Standard Time (AST) at UTC−4 during the fall and winter months, and shifts to Atlantic Daylight Time (ADT) at UTC−3 during daylight saving time, where applicable. Major regions using Atlantic Time include Nova Scotia, New Brunswick, Puerto Rico, and the U.S. Virgin Islands.

Importance and Global Use of Atlantic Time

Atlantic Time is important for regional coordination across eastern Canada and several Caribbean territories. In provinces like Nova Scotia and New Brunswick, it supports government services, commerce, and broadcasting, while aligning timekeeping with the Atlantic region's seasonal shifts. In other areas like Puerto Rico, which does not observe daylight saving time, AST provides a consistent year-round time reference.

The time zone also plays a role in international communications and logistics, particularly between North America and South America, and among island nations in the Atlantic basin. Its use across both fixed and daylight-adjusting regions highlights the flexibility and importance of AT in synchronizing transportation, trade, and digital services across borders.

Where and When AT is used worldwide

North America

Canadian provinces using AST during winter and ADT during summer:

• Most of mainland Labrador, in the province of Newfoundland and Labrador InfoLabrador's southeastern coast and the island of Newfoundland follow NST/NDT time zones.
• New Brunswick
• Nova Scotia
• Prince Edward Island

Areas of Greenland using AST during winter and ADT during summer:

• Thule Air Base

Canadian provinces using AST all year:

• Quebec (areas east of 63°W longitude)

Atlantic

Atlantic islands and territories using AST during winter and ADT during summer:

• Bermuda

Caribbean

Caribbean countries and territories using AST all year:

• Anguilla
• Antigua and Barbuda
• Aruba
• Barbados
• British Virgin Islands
• Caribbean Netherlands
• Curaçao
• Dominica
• Dominican Republic
• Grenada
• Guadeloupe
• Martinique
• Montserrat
• Puerto Rico
• Saint Barthélemy
• Saint Kitts and Nevis
• Saint Lucia
• Saint Martin (FR)
• Saint Vincent and the Grenadines
• Sint Maarten (NL)
• Trinidad and Tobago
• U.S. Virgin Islands