Time zone · Americas
AST
Atlantic Standard Time
Atlantic Standard Time (AST, UTC−04:00) covers a broad swath of the Caribbean and parts of eastern Canada, where most islands stay on a steady year-round clock while six northern zones (four in Atlantic Canada, plus Bermuda and Pituffik in Greenland) move to Atlantic Daylight Time in summer.
Wednesday, October 14, 2026
Current offset
UTC-04:00
Standard · AST
Daylight saving
Not active
Year-round standard time
IANA zones
29
6 observe DST, 23 don't
DST offset
UTC-03:00
ADT · +1h
About AST
Standard time, with a summer shift.
Atlantic Standard Time (AST, UTC−04:00) covers a broad swath of the Caribbean and parts of eastern Canada, where most islands stay on a steady year-round clock while six northern zones (four in Atlantic Canada, plus Bermuda and Pituffik in Greenland) move to Atlantic Daylight Time in summer.
IANA zones · the technical identifiers
The 29 zones that resolve to AST.
For software, always store the IANA identifier — never the abbreviation alone. The database keeps these zones distinct because their rules can, and historically did, diverge.
Cities across AST
Local time, city by city.
26 cities
Where AST is used
25 countries.
Same offset · UTC-04:00
Other zones at UTC-04:00 right now.
These named zones share AST's offset today. When daylight saving rules differ, they drift apart for part of the year.
Convert
AST to the world's clocks.
Frequently asked questions
Common questions about AST, daylight saving, and how to handle it in software. Can't find what you need? Email [email protected].
- Why do most AST zones never change their clocks?
- Most Caribbean islands near the equator see very little variation in daylight throughout the year, so they keep a fixed offset (UTC−04:00) and skip daylight saving entirely.
- Which AST areas do observe daylight saving?
- Six zones do: Nova Scotia, Prince Edward Island, New Brunswick and most of Labrador in Canada, plus Bermuda and Pituffik (Thule) in Greenland. They switch to Atlantic Daylight Time (ADT, UTC−03:00) in summer. Quebec’s AST area around Blanc-Sablon stays on UTC−04:00 all year.
- How many time zones share the AST code?
- There are 29 member zones under the AST umbrella, spanning independent nations, overseas territories, and Canadian provinces.
- Is AST the same as Eastern Standard Time?
- No. AST is one hour ahead of EST (UTC−05:00) and aligns with EDT (UTC−04:00) only when Eastern Time is observing daylight saving.
- Why does Anguilla never observe DST?
- Anguilla’s location in the Caribbean means nearly equal day and night year-round, so there’s little benefit to shifting clocks.
- What’s the historical origin of AST?
- Halifax adopted Atlantic Standard Time in 1902, and Puerto Rico in 1899. The other Caribbean members settled on UTC−04:00 at various dates during the 20th century.
- Do all AST countries share the same date for time changes?
- No. Only the six zones that observe daylight saving (in Atlantic Canada, Bermuda and Pituffik in Greenland) change clocks, on the North American dates; the rest stay fixed.
- How does AST affect travel between islands?
- Travel between most AST islands doesn’t require clock adjustments, but flying to or from the Maritimes, Labrador, Bermuda or Pituffik in summer means a one-hour shift.
Source: IANA tzdb2026d · Reviewed
Free · Developer API
This time zone, as JSON.
Its defining offset, DST status and member counts, from one endpoint.
Also in the API: time zones by coordinates, conversions that flag daylight saving gaps, and abbreviations decoded.
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