Atlantic Standard Time (AST): Offset and Places
Get a clear, accurate explanation with examples and useful comparisons. Atlantic Standard Time (AST): Offset and Places.
Atlantic Standard Time (AST): Offset and Places
Quick answer
Atlantic Standard Time (AST) is UTC−04:00. Puerto Rico and the US Virgin Islands remain on AST all year; Halifax normally switches to Atlantic Daylight Time (ADT) for summer.
To read the hour in Atlantic Standard Time accurately, select the city and its IANA time zone in a live clock. A date-aware clock accounts for seasonal changes where they apply. The dated examples below explain how the offsets work during different parts of 2026.
Which local time zone should you use?
Different cities and regions may or may not share the same clock. The table uses each city’s civil time zone, which is more reliable than assigning a whole country one fixed number.
| City or region | IANA time zone | Jan 15, 2026 | Jul 15, 2026 |
| San Juan, Puerto Rico | America/Puerto_Rico | UTC−04:00 | UTC−04:00 |
| Halifax, Nova Scotia | America/Halifax | UTC−04:00 | UTC−03:00 |
| St. Thomas, USVI | America/St_Thomas | UTC−04:00 | UTC−04:00 |
Worked time examples with an exact date
A single UTC instant translates to different local clock readings. Each example starts at 2:00 p.m. UTC on the date stated, making seasonal differences easy to compare.
San Juan, Puerto Rico: January 15, 2026 → Thu Jan 15, 10:00 AM AST (UTC−04:00); July 15, 2026 → Wed Jul 15, 10:00 AM AST (UTC−04:00).
Halifax, Nova Scotia: January 15, 2026 → Thu Jan 15, 10:00 AM AST (UTC−04:00); July 15, 2026 → Wed Jul 15, 11:00 AM ADT (UTC−03:00).
St. Thomas, USVI: January 15, 2026 → Thu Jan 15, 10:00 AM AST (UTC−04:00); July 15, 2026 → Wed Jul 15, 10:00 AM AST (UTC−04:00).
How it compares with New York
| New York reference | Time in San Juan, Puerto Rico |
| January 15, 2026 at 9:00 AM ET | January 15 at 10:00 AM (AST) |
| July 15, 2026 at 9:00 AM ET | July 15 at 9:00 AM (AST) |
| November 15, 2026 at 9:00 AM ET | November 15 at 10:00 AM (AST) |
As these dated conversions show, a time difference can change during the year if the two places use different daylight-saving rules. Do not assume “Atlantic Time” and “AST” have identical meaning: Atlantic Time can refer to a region that alternates AST and ADT.
Useful scheduling checks
An event in San Juan and an event in Halifax may be on different local times during part of the year.
For a meeting, flight, livestream or delivery in Atlantic Standard Time, keep the city, local date and time-zone label together. A calendar invitation that includes the correct time-zone identifier can adjust for daylight saving automatically; a plain text message saying “3 PM” cannot.
A reliable way to read the current time
Choose a live clock configured to the correct IANA zone (for example, “America/Puerto_Rico”), verify the displayed date as well as hour, and check whether the calendar event is fixed to a city or to your device’s time zone. A time-zone abbreviation without a date can be ambiguous around seasonal transitions.
Frequently asked questions
Do all places in Atlantic Standard Time use the same time?
The locations listed in the zone table show the important local distinctions. Check a specific city if you are traveling across a regional boundary.
What UTC offset does Atlantic Standard Time use?
It depends on the city and, where daylight saving is observed, the date. The dated January and July offsets above show the distinction for 2026.
Why is the local time different from New York?
UTC offsets and daylight-saving schedules control the difference. New York changes from EST to EDT, while the destination may follow another rule or remain fixed all year.
Related time guides
These related guides answer adjacent questions without repeating the focus of this page:
Current Time in Puerto Rico: San Juan and AST