AST can mean 2 different things depending on where you are: Atlantic Standard Time (UTC-4); Arabia Standard Time (UTC+3). Each is explained below.
AST stands for Atlantic Standard Time and is UTC-4, which is 4 hours behind UTC.
Some of these places also switch to ADT (UTC-3) while daylight saving time is in effect. Others keep AST all year.
Cities that use AST: Santo Domingo, San Juan, Halifax, Bridgetown, Port of Spain, Basseterre, Castries, Roseau, St. George's, Willemstad, Oranjestad, Road Town, Fort-de-France, Pointe-à-Pitre and 2 more.
| When it is… | 9:00 AM AST | 12:00 PM AST | 5:00 PM AST |
|---|---|---|---|
| UTC | 1:00 PM | 4:00 PM | 9:00 PM |
| PST (Pacific) | 5:00 AM | 8:00 AM | 1:00 PM |
| MST (Mountain) | 6:00 AM | 9:00 AM | 2:00 PM |
| CST (Central US) | 7:00 AM | 10:00 AM | 3:00 PM |
| EST (Eastern) | 8:00 AM | 11:00 AM | 4:00 PM |
| CET (Central Europe) | 2:00 PM | 5:00 PM | 10:00 PM |
| EET (Eastern Europe) | 3:00 PM | 6:00 PM | 11:00 PM |
| IST (India) | 6:30 PM | 9:30 PM | 2:30 AM (+1 day) |
| JST (Japan) | 10:00 PM | 1:00 AM (+1 day) | 6:00 AM (+1 day) |
| AEST (Sydney) | 11:00 PM | 2:00 AM (+1 day) | 7:00 AM (+1 day) |
AST stands for Arabia Standard Time and is UTC+3, which is 3 hours ahead of UTC.
This abbreviation is also used informally for Arabia Standard Time. The time zone database does not use it, so check the context.
| When it is… | 9:00 AM AST | 12:00 PM AST | 5:00 PM AST |
|---|---|---|---|
| UTC | 6:00 AM | 9:00 AM | 2:00 PM |
| PST (Pacific) | 10:00 PM (-1 day) | 1:00 AM | 6:00 AM |
| MST (Mountain) | 11:00 PM (-1 day) | 2:00 AM | 7:00 AM |
| CST (Central US) | 12:00 AM | 3:00 AM | 8:00 AM |
| EST (Eastern) | 1:00 AM | 4:00 AM | 9:00 AM |
| CET (Central Europe) | 7:00 AM | 10:00 AM | 3:00 PM |
| EET (Eastern Europe) | 8:00 AM | 11:00 AM | 4:00 PM |
| IST (India) | 11:30 AM | 2:30 PM | 7:30 PM |
| JST (Japan) | 3:00 PM | 6:00 PM | 11:00 PM |
| AEST (Sydney) | 4:00 PM | 7:00 PM | 12:00 AM (+1 day) |
AST can stand for Atlantic Standard Time; Arabia Standard Time.
Atlantic Standard Time is UTC-4. Arabia Standard Time is UTC+3.
AST is UTC-4 and ADT is UTC-3, a difference of 1 hour. Places that use both switch between them when daylight saving time starts and ends. The live line above shows which one applies right now.
It depends on context. Look at the place or the schedule the abbreviation comes from, or ask for the UTC offset to be written out, such as UTC+8 instead of CST.