- BCE - Before the Common Era
- CE - Common Era
- Lunisolar - Calendar used by China, Japan and Korea prior to 1912, 1873 and 1896 respectively.
- Ma - Million Years Ago
- Kya - Thousand Years Ago
- NS - "New Style" indicates that a date conforms to the Gregorian calendar.
- O.S. - or OS indicates that a date conforms to the Julian calendar.