| AD | In English, Anno Domini. Equivalent to "after Christ". |
| BC | In English, Before Christ. Equivalent to "before Christ". |
| BE | Buddhist Era (Thailand), or phutthasakarat. |
| CE | In English, Common Era. Equivalent to AD (for those who prefer not to refer to Christ). |
| BCE | In English, Before the Common Era. Equivalent to BC (for those who prefer not to refer to Christ). |
| JD | In English, Julian Day. Julian-day count in the Julian period. |
| MJD | In English, Modified Julian Day. |
| DJM | Modified Julian Date. |
| AM | Hebrew year. Anno Mundi: year of the world. = 3761 BC |
| AH | Islamic year. Anno Hegirae, or year of the Hijra. = 16 July 622 AD |
| S | Solar Hijri calendar (Iran and Afghanistan) |
| AC | Ab Urbe Condita (from the founding of Rome) |
| BP | Before Present (before 1950) |
| GMT | Greenwich Mean Time |
| TAI | International Atomic Time |
| TE | Ephemeris Time |
| UT (TU) | Universal Time |
| UTC | Coordinated Universal Time |
| DST | Daylight Saving Time (summer/winter clock change system) |
