AST is used for 2 different time zones. The table below shows each one with its offset and current time.
What AST can mean
The letters AST are shared by zones on different offsets. A meeting invite that says only AST can be read several ways, so add a city name or a UTC offset.
| Name | UTC offset | Time now | Used in |
|---|---|---|---|
| Atlantic Standard Time | UTC−4 | --:-- | America/Halifax, America/Puerto_Rico, America/Santo_Domingo, Atlantic/Bermuda |
| Arabian Standard Time | UTC+3 | --:-- | Asia/Riyadh, Asia/Baghdad, Asia/Kuwait, Asia/Qatar |
Who uses AST
| IANA time zone | Uses AST | Main cities |
|---|---|---|
| America/Halifax | Outside daylight saving time | Halifax, Dartmouth |
| America/Puerto_Rico | All year | San Juan, Bayamón, Carolina |
| America/Santo_Domingo | All year | Santo Domingo, Santiago de los Caballeros, Santo Domingo Oeste |
| Atlantic/Bermuda | Outside daylight saving time | Hamilton |
| Asia/Riyadh | All year | Jeddah, Riyadh, Mecca |
| Asia/Baghdad | All year | Baghdad, Mosul, Erbil |
| Asia/Kuwait | All year | Al Ahmadi, Hawalli, Sabah Al Salem |
| Asia/Qatar | All year | Doha, Al Rayyan, Lusail |
AST and ADT
ADT is the daylight saving version of AST, 1 hour ahead of it. Writing AST in summer means a time that is 1 hour off for the places that have switched.
Tools for time in AST
- Convert a time to or from AST: pick a date and time and see it in every city on your list.
- Add Halifax to your world clock to keep it next to your own time.
- Find a meeting time that falls inside office hours in AST and the other cities you work with.
- Open a full-screen clock for your own time zone.
Frequently asked questions
Is it AST or ADT right now?
AST is in use now in Halifax, San Juan, Santo Domingo and Hamilton. ADT returns on Sunday, March 14, 2027.
Which time zone does AST mean?
It depends on who wrote it. Atlantic Standard Time (UTC−4): Halifax, San Juan, Santo Domingo and Hamilton; Arabian Standard Time (UTC+3): Jeddah, Baghdad, Al Ahmadi and Doha. Ask for a city or a UTC offset if the context does not make it clear.
What time is 12:00 AST in UTC?
12:00 AST is 4:00 PM UTC.
Time zone rules: IANA tz database, version 2026e. Place names and coordinates: GeoNames. Sunrise and sunset are calculated from the coordinates and can differ by a minute or two from local almanacs.