Atlantic Time is UTC-4 in standard time (AST) and UTC-3 during daylight saving (ADT).
Atlantic Time
- AST: UTC minus 4 (standard time).
- ADT: UTC minus 3 (daylight time).
Where
Nova Scotia, New Brunswick, Prince Edward Island, parts of Quebec’s Lower North Shore, Puerto Rico and the US Virgin Islands. Puerto Rico stays on AST all year.
Compared with Eastern
Atlantic Time is 1 hour ahead of Eastern Standard Time.
DST
Canada observes daylight time between March and November.
Standard time zone
Atlantic Standard Time (AST) is UTC minus 4 hours. During daylight saving time, Atlantic Daylight Time (ADT) is UTC minus 3.
Where it is used
- Canada: Nova Scotia, New Brunswick, Prince Edward Island, most of Labrador and the Lower North Shore of Quebec. The island of Newfoundland uses its own half hour offset (UTC minus 3:30).
- Caribbean: Puerto Rico, the US Virgin Islands, the Dominican Republic, Barbados, Trinidad and Tobago and many others, which use AST all year.
- Bermuda, which observes daylight saving time.
- Greenland: Thule Air Base and the Qaanaaq area.
Compared with Eastern time
In winter, Atlantic Standard Time is 1 hour ahead of Eastern Standard Time (for example, Halifax versus New York). In summer, Halifax is on ADT (UTC minus 3), still 1 hour ahead of New York on EDT (UTC minus 4). Puerto Rico stays on UTC minus 4 all year, so it matches New York in summer and is 1 hour ahead in winter.
Daylight saving
Canadian Atlantic provinces and Bermuda follow DST from the second Sunday in March to the first Sunday in November. Puerto Rico, the US Virgin Islands and the Dominican Republic do not.
How to check
Use a world clock or phone settings and search for the city, such as Halifax or San Juan, to get the current local time.
Time zone names
The abbreviation AST is also used for Arabia Standard Time, so write out the zone name in scheduling.
Meeting tips
When scheduling with someone in Puerto Rico, remember that the offset from the US East coast changes with daylight saving.
Atlantic Standard Time in numbers
Atlantic Standard Time (AST) is UTC minus 4 hours. During daylight saving, places that observe it move to Atlantic Daylight Time (ADT), UTC minus 3. Eastern Canadian provinces Nova Scotia, New Brunswick and Prince Edward Island, along with Bermuda, observe daylight saving, while Puerto Rico, the US Virgin Islands, the Dominican Republic and Barbados stay on UTC minus 4 all year. Newfoundland uses its own half hour offset, UTC minus 3:30 in standard time. Labrador mostly follows Atlantic time.
Practical conversions
When it is noon in Halifax in winter, it is 11 a.m. in New York, 8 a.m. in Los Angeles and 4 p.m. in London. In summer London is on British Summer Time, so Halifax is 4 hours behind. Because Puerto Rico does not change clocks, its gap with New York is 1 hour in winter and 0 in summer. For scheduling across zones, use the IANA name such as America/Halifax or America/Puerto_Rico in calendar software to avoid daylight saving errors.
Based on data from the IANA Time Zone Database and the National Research Council Canada
