ADT — Atlantic Daylight Time
ADT is Atlantic Daylight Time, 3 hours behind UTC. It is a fixed offset: unlike a time zone, it does not change with the season — the zones that use it switch to a different abbreviation instead.
Current time in ADT
04:46
Sunday, 2 August 2026
ADT = UTC-3 · 3 hours behind UTC
Shown for 2 Aug 2026 07:46 UTC. The clock goes live as soon as scripts load.
UTC offset
UTC-3
Type
Daylight saving
Seasonal counterpart
AST
The letters the same zones use for the other half of the year
Meanings
1
Unambiguous
Is ADT in force right now?
A zone only carries this abbreviation for part of the year. This is which of them were on it at 2 Aug 2026 07:46 UTC; the list is re-derived against your own clock when scripts load.
On ADT now
- America/Halifax — Halifax
Using a different abbreviation
- Every zone listed here was on ADT.
ADT alternates with AST across the year.
Writing “ADT” for a date in the other half of the year is the most common time zone mistake in meeting invitations.
Convert ADT to other time zones
City clocks reflect whatever their zone is doing; where a city observes daylight saving time, its difference from ADT changes twice a year. Use the time zone converter for a specific date.
Time zones and cities that use ADT
Atlantic Daylight Time · UTC-3
Why ADT is not an identifier
ADT is shorthand, not a standard. There is no registry of time zone abbreviations, no authority that assigns them, and nothing preventing two regions from adopting the same three letters — which is what makes codes like IST and CST unusable without context.
For anything a machine will read — a calendar invitation, a database column, an API response — use the IANA identifier of the zone (America/Halifax, for example) or an explicit UTC offset alongside the date. The identifier survives a change in the law; ADT and its 3 hours offset do not.
Abbreviations on the same clock
Frequently asked questions
What does ADT stand for?
ADT stands for Atlantic Daylight Time. It is 3 hours behind UTC, written UTC-3.
What is ADT in UTC?
ADT is UTC-3. To convert an ADT time to UTC, add 3 hours.
What is the difference between ADT and AST?
ADT is the daylight saving form and AST the standard form of the same zones. The two are one hour apart and only one is ever in force at a time, so a recurring meeting written "ADT" shifts by an hour when the clocks change.
Which time zone should I use instead of ADT?
Use an IANA identifier — America/Halifax for Atlantic Daylight Time — or state the UTC offset with the date. Abbreviations are not identifiers: they are not unique, they are not registered anywhere, and half of them change with the season. Calendar software resolves this automatically when you pick a city rather than typing letters.