Multiple Global Meanings for AST
The abbreviation AST has multiple official meanings across different continents and legal jurisdictions. Below are all recognized global definitions:
Region: North America & Caribbean
Daylight Saving: Observes DST (shifts to ADT)
Region: Middle East (Saudi Arabia, Qatar, Kuwait, Bahrain, Iraq, Yemen)
Daylight Saving: No daylight saving shift
Technical Specifications & Standards
Official chronometric properties, ISO standards, and international database registry identifiers for Atlantic Standard Time:
Daylight Saving Time (DST) Transitions
⬆️ Spring Forward (Clocks Advance)
Second Sunday in March at 02:00 AM (Maritime Canada and Bermuda advance to ADT)
⬇️ Fall Back (Clocks Return)
First Sunday in November at 02:00 AM (Maritime Canada and Bermuda return to AST)
Observing Jurisdictions & Subdivisions
32 Sovereign NationsSovereign nations, administrative subdivisions, and regional territories officially operating under AST:
Regional Subdivisions & Territory Details
Financial Markets & Trading Hours
Atlantic time operates one hour ahead of Wall Street, bridging European late afternoons with North American trading desks.
Local Hours: 09:00 - 16:00 AST
UTC Window: 13:00 - 21:00 UTC
Local Hours: 09:00 - 15:00 AST
UTC Window: 13:00 - 21:00 UTC
Local Hours: 10:00 - 13:00 AST
UTC Window: 13:00 - 21:00 UTC
Major Cities in AST
Primary metropolitan centers and financial hubs observing this time zone:
Adoption History & Astronomical Facts
Year Established: 1883
Adopted by Canadian rail networks in 1883 as Intercolonial Time, based on the 60th meridian west passing directly through the Gulf of St. Lawrence and the eastern tip of Cape Breton Island.
Puerto Rico and the US Virgin Islands have remained on Atlantic Standard Time without daylight saving adjustments since the Uniform Time Act of 1966 granted states and territories the right to opt out.
Frequently Asked Questions about AST
What is the difference between AST and EST?
Atlantic Standard Time is one hour ahead of Eastern Standard Time. When it is 12:00 noon in New York (EST), it is 1:00 PM in Halifax and San Juan (AST).
Does Puerto Rico change clocks for Daylight Saving Time?
No. Puerto Rico stays on Atlantic Standard Time (UTC-4) throughout the entire year, meaning it shares the exact same clock time as New York and Toronto during North American summer (EDT).
Can AST refer to time zones outside the Americas?
Yes. In meteorology, aviation, and Middle Eastern business, AST frequently denotes Arabia Standard Time (UTC+3), observed in Saudi Arabia, Qatar, Bahrain, Kuwait, and Iraq.