Convert SGT to AST
AST is 12 hours behind SGT. SGT is UTC+8 and AST is UTC−4.
Right now: SGT · AST
Which AST is this?
AST names more than one zone. This page reads it as Atlantic Standard Time at UTC−4, which is the reading most converters take. There is one other: Arabia Standard Time at UTC+3, used in Saudi Arabia, Iraq, Kuwait, Bahrain, Qatar and Yemen.
The letters on a meeting invitation do not say which one is meant. If yours is not Atlantic Standard Time, the answer above is wrong, and not by a little:
| If AST means | Then |
|---|---|
| Atlantic Standard Time — assumed on this page | AST is 12 hours behind SGT |
| Arabia Standard Time | AST is 5 hours behind SGT |
The large converter sites disagree about this as well: search for a AST conversion and some of the results answer for one reading and some for another, none of them saying which they chose. Where it matters, ask which country the sender is in rather than which letters they typed.
Best time to schedule a meeting
Standard 9–5 working hours do not overlap at all between SGT and AST. Someone has to take an early or late call — or use asynchronous communication instead.
| SGT | AST | Suitable? |
|---|---|---|
| 9:00 AM | 9:00 PM (previous day) | outside 9–5 |
| 10:00 AM | 10:00 PM (previous day) | outside 9–5 |
| 11:00 AM | 11:00 PM (previous day) | outside 9–5 |
| 12:00 PM | 12:00 AM | outside 9–5 |
| 1:00 PM | 1:00 AM | outside 9–5 |
| 2:00 PM | 2:00 AM | outside 9–5 |
| 3:00 PM | 3:00 AM | outside 9–5 |
| 4:00 PM | 4:00 AM | outside 9–5 |
| 5:00 PM | 5:00 AM | outside 9–5 |
SGT to AST conversion table
| SGT | AST |
|---|---|
| 12:00 AM | 12:00 PM (previous day) |
| 1:00 AM | 1:00 PM (previous day) |
| 2:00 AM | 2:00 PM (previous day) |
| 3:00 AM | 3:00 PM (previous day) |
| 4:00 AM | 4:00 PM (previous day) |
| 5:00 AM | 5:00 PM (previous day) |
| 6:00 AM | 6:00 PM (previous day) |
| 7:00 AM | 7:00 PM (previous day) |
| 8:00 AM | 8:00 PM (previous day) |
| 9:00 AM | 9:00 PM (previous day) |
| 10:00 AM | 10:00 PM (previous day) |
| 11:00 AM | 11:00 PM (previous day) |
| 12:00 PM | 12:00 AM |
| 1:00 PM | 1:00 AM |
| 2:00 PM | 2:00 AM |
| 3:00 PM | 3:00 AM |
| 4:00 PM | 4:00 AM |
| 5:00 PM | 5:00 AM |
| 6:00 PM | 6:00 AM |
| 7:00 PM | 7:00 AM |
| 8:00 PM | 8:00 AM |
| 9:00 PM | 9:00 AM |
| 10:00 PM | 10:00 AM |
| 11:00 PM | 11:00 AM |
About SGT
Singapore Time (SGT) is UTC+8. It is used in Singapore and Malaysia.
Singapore Time is UTC+8 with no daylight saving. The offset is a historical curiosity: Singapore sits at about 104°E, which is geographically UTC+7, and moved to +8 in 1982 to align with Malaysia and Hong Kong for trade. The result is that the sun is at its highest around 1pm rather than noon, and sunrise is late all year.
About AST
Atlantic Standard Time (AST) is UTC−4. It is used in Halifax, Puerto Rico and the eastern Caribbean in winter.
Atlantic Standard Time is UTC−4, one hour ahead of Eastern. It covers Canada's Atlantic provinces, Puerto Rico and much of the eastern Caribbean, and it is the reason a call from Halifax to Toronto is an hour out from what either party expects. The abbreviation is also used for Arabia Standard Time at UTC+3, seven hours away in the other direction, which is a genuinely dangerous collision in scheduling.
Does this gap change with the seasons?
Neither SGT nor AST shifts with the seasons, so this 12-hour difference holds all year. That is unusual enough to be worth relying on: most cross-continental gaps move twice a year.
This is the reason scheduling systems store an IANA zone such as Region/City rather than an offset or an abbreviation: the zone knows its own rules and the offset does not.
Frequently asked questions
What time is 9:00 AM SGT in AST?
9:00 AM SGT is 9:00 PM AST (previous day).
Is AST ahead of SGT?
AST is 12 hours behind SGT.
Which time zone does this use?
SGT is UTC+8 and AST is UTC−4. Both abbreviations denote a single fixed offset, so this conversion never shifts with daylight saving — what changes is which abbreviation a place is using at the time.