ADT — Atlantic Daylight Time
Learn what ADT means, where Atlantic Daylight Time is used, how it relates to AST, and convert it with other time zones.
Meaning and countries used
ADT stands for Atlantic Daylight Time and is UTC-3. It is used during daylight saving time in Bermuda and parts of Canada.
DST and AST relationship
ADT is the daylight saving counterpart to AST. When DST is active, clocks move from Atlantic Standard Time (UTC-4) to ADT (UTC-3).
Convert ADT with others
Compare ADT with other time zones using visual time grids and hour-by-hour tables. Export meetings with ICS download or share via Google Calendar and Gmail.
How to Convert ADT to Other Time Zones
Looking for Arabia Daylight Time? See /time-converter/adt-arabia-time-zone.
Open the ADT converter page: Visit
https://www.xconvert.com/time-converter/adt-time-zoneto load ADT (Atlantic Daylight Time, UTC-3) as the starting reference on the visual comparison grid. This view is useful when you are scheduling a call with contacts in Halifax, Hamilton, or Fredericton, or planning work across Bermuda and Atlantic Canada where ADT is used.Add comparison cities: Click + Add City and search for cities you want to compare against Atlantic Daylight Time. A practical setup is to add Atlantic Daylight Time locations such as Halifax, Charlottetown, or Happy Valley-Goose Bay so you can line up work hours across regional offices, travel plans, or customer support coverage in Bermuda and Canada.
Select a time range on the grid: Click Select to enter selection mode, then drag across the colored timeline in the ADT row to highlight a meeting window in purple. You can drag the center of the selection to move it or use the left and right handles to resize it, which is helpful when narrowing down a business call window that stays inside green work-hour blocks for Atlantic Daylight Time cities.
Export and share the result: Once a range is selected, use the export options for ICS download, Google Calendar, Gmail, Copy to clipboard, or Share link. This is useful for sending a confirmed Atlantic Daylight Time meeting slot to a distributed team so everyone receives the same time block in a calendar-friendly format.
About Atlantic Daylight Time (ADT)
ADT (Atlantic Daylight Time, UTC-3) is the daylight saving time abbreviation used in parts of Bermuda and Canada. It is commonly associated with Atlantic-region locations including Charlottetown, Dartmouth, Dieppe, Fredericton, Glace Bay, Halifax, Hamilton, Happy Valley-Goose Bay, Labrador City, and Lower Sackville.
Atlantic Daylight Time is specifically the daylight saving counterpart of AST. When ADT is in effect, clocks are observed at UTC-3 rather than under its standard-time counterpart abbreviation, AST.
Countries that use Atlantic Daylight Time include Bermuda and Canada. For people coordinating meetings, transport, or regional operations, that means ADT is especially relevant for Atlantic Canadian cities and Bermuda-based schedules.
Atlantic Daylight Time also shares the same UTC offset as several other abbreviations, including AMST, ART, AT, BRT, CLST, FKST, GFT, P, PMST, PYST, PYT, ROTT, SRT, UYT, WARST, and WGT. Even when the offset matches, the abbreviation matters because regional naming and daylight-saving context differ across countries and territories.
ADT and Daylight Saving Time
Atlantic Daylight Time is itself a daylight saving time abbreviation rather than a year-round standard time zone label. Its standard counterpart is AST, so ADT is the form used during the daylight saving portion of the year, while AST is used outside that period.
This distinction matters when reading schedules, tickets, or calendar invites for Bermuda and Canada. If an event is labeled in Atlantic Daylight Time, it is using UTC-3 and should not be treated as the same abbreviation as AST, even though the two are directly related as seasonal counterparts.
For recurring business meetings, payroll cutoffs, and travel itineraries, the key practical point is that Atlantic Daylight Time changes seasonally and then reverts to AST. When comparing times across regions, always confirm whether a schedule is using the daylight abbreviation ADT or the standard abbreviation AST before sending invitations or confirming attendance.
Frequently Asked Questions
What does ADT stand for?
ADT stands for Atlantic Daylight Time. It is a daylight saving time abbreviation with an exact offset of UTC-3 and is used in Bermuda and parts of Canada.
Is ADT the same as AST?
No, Atlantic Daylight Time is not the same as AST. ADT is the daylight saving abbreviation at UTC-3, while AST is its standard-time counterpart used outside the daylight saving period.
Which cities use ADT?
Atlantic Daylight Time is used in places associated with cities such as Charlottetown, Dartmouth, Dieppe, Fredericton, Glace Bay, Halifax, Hamilton, Happy Valley-Goose Bay, Labrador City, and Lower Sackville. These locations make ADT especially relevant for regional scheduling across Atlantic Canada as well as Bermuda.
What is the UTC offset for ADT?
Atlantic Daylight Time uses UTC-3. That offset places it three hours behind Coordinated Universal Time during the daylight saving period when ADT is in effect.
When does ADT change?
Atlantic Daylight Time is the daylight saving form of the Atlantic time designation, and it changes back to AST as part of the seasonal switch. The key relationship is that ADT is the daylight saving abbreviation and AST is the standard counterpart, so schedules should be read carefully when the season changes.
Is ADT Atlantic Daylight Time or Arabia Daylight Time?
On this page, ADT means Atlantic Daylight Time, which uses UTC-3. ADT can also refer to Arabia Daylight Time, which uses UTC+4; if you need that meaning, use /time-converter/adt-arabia-time-zone.
Which countries use Atlantic Daylight Time?
Atlantic Daylight Time is used in Bermuda and Canada. That makes it relevant for cross-border scheduling involving Atlantic Canadian cities and Bermuda-based business, travel, or customer communications.