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 keeps business hours aligned across Halifax, St. John’s airspace, Bermuda’s financial market, and even remote stations in Greenland’s far north.
Friday, June 5, 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 keeps business hours aligned across Halifax, St. John’s airspace, Bermuda’s financial market, and even remote stations 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 currently on ADT
The same hour, city by city.
1 city · all UTC-03:00
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.
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?
- Stretching from Nova Scotia to Bermuda to Thule, all six ADT member zones spring forward in March and fall back in November on almost identical schedules. This alignment simplifies air travel along the North Atlantic, financial trading with U.S. East Coast markets, and military co-operation out of Thule Air Base.
- 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?
- Currently, 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, St. John’s, Bermuda’s capital Hamilton, and the remote town of Qaanaaq in Greenland.
- Do all ADT zones change clocks at the same local moment?
- The switches happen simultaneously in UTC, but because each zone’s ‘wall clock’ differs by an hour or two, the local clock reading at the moment of change varies from place to place.
- How does ADT compare with U.S. Eastern daylight time?
- ADT is actually equivalent to U.S. Eastern Daylight Time: both are UTC-03:00 from March to November. That parity makes cross-border meetings between Toronto, New York, and Halifax easy to schedule.
Free · Developer API
Time, as JSON.
Every IANA time zone with live offsets, DST status, and the countries and cities that use them — clean, dependable JSON. Sign up free and get an API key in seconds.
countries, cities, convert, DST transitions coming next.
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