Time zone · Americas
ADT
Atlantic Daylight Time
Atlantic Daylight Time (ADT) is the broad daylight-saving offset shared by six Atlantic zones across eastern Canada, Greenland, and Bermuda. It covers Halifax, Moncton, Glace Bay and Goose Bay in Atlantic Canada, Bermuda, and Pituffik Space Base (formerly Thule Air Base) in Greenland’s far north.
Wednesday, October 14, 2026
Current offset
UTC-03:00
Daylight · ADT
Daylight saving
Active
Reverts 1 Nov 2026
IANA zones
6
6 observe DST, 0 don't
DST offset
—
No summer variant
About ADT
Standard time, with a summer shift.
Atlantic Daylight Time (ADT) is the broad daylight-saving offset shared by six Atlantic zones across eastern Canada, Greenland, and Bermuda. It covers Halifax, Moncton, Glace Bay and Goose Bay in Atlantic Canada, Bermuda, and Pituffik Space Base (formerly Thule Air Base) in Greenland’s far north.
IANA zones · the technical identifiers
The 6 zones that resolve to ADT.
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 ADT
Local time, city by city.
1 city
Where ADT is used
3 countries.
Same offset · UTC-03:00
Other zones at UTC-03:00 right now.
These named zones share ADT's offset today. When daylight saving rules differ, they drift apart for part of the year.
Convert
ADT to the world's clocks.
Frequently asked questions
Common questions about ADT, daylight saving, and how to handle it in software. Can't find what you need? Email [email protected].
- Why do Canadian Maritimes, Greenland, and Bermuda all share ADT?
- All six zones use UTC-04:00 as standard time and follow the North American daylight saving rules, moving to UTC-03:00 on the second Sunday in March and back on the first Sunday in November. The group covers Nova Scotia, Prince Edward Island, New Brunswick, Labrador, Bermuda and Pituffik (Thule) in northwest Greenland.
- How does ADT work in practice?
- During the summer half of the year—from the second Sunday in March to the first Sunday in November—clocks in the ADT region are shifted one hour ahead to UTC-03:00. The rest of the year they revert to Atlantic Standard Time at UTC-04:00.
- Can any ADT zone opt out of daylight saving?
- Every member zone observes DST, so the region is fully synchronized during the transition window.
- Which major cities are in the ADT region?
- Halifax, Nova Scotia, is the most prominent, but ADT also covers Moncton, Saint John, Glace Bay, Goose Bay, Bermuda’s capital Hamilton, and Pituffik Space Base (formerly Thule Air Base) in northwest Greenland.
- Do all ADT zones change clocks at the same local moment?
- Yes. Every ADT zone switches at 2:00 a.m. local time, and because they all share the same clock (UTC-04:00 in winter, UTC-03:00 in summer), that is the same moment across the whole region.
- How does ADT compare with U.S. Eastern daylight time?
- ADT is one hour ahead of U.S. Eastern Daylight Time (UTC-04:00). Both switch on the same dates, so Halifax stays one hour ahead of Toronto and New York all year.
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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