| Abbreviation | Definition |
|---|---|
| AM | Ante Meridiem |
| AMST | Amazon Summer Time |
| AMST | Armenia Summer Time |
| AMT | Amazon Time |
| AMT | Armenia Time |
| ANAST | Anadyr Summer Time |
| ANAT | Anadyr Time |
| AOE | Anywhere On Earth |
| ART | Argentina Time |
| AST | Alaskan Standard Time [UTC - 1000] |
| AST | Arabia Standard Time |
| AST | Arabian Standard Time |
| AST | Atlantic Daylight Saving Time |
| AST | Atlantic Standard Time [UTC - 0400] |
| AWST | Australian Western Standard Time (UTC + 0800) |
| AZOST | Azores Summer Time |
| AZOT | Azores Time |
| AZST | Azerbaijan Summer Time |
| AZT | Azerbaijan Time |
| B | Bering Standard Time [UTC - 1100] |