Calendar era
A calendar era is the year numbering system used by a calendar. The Gregorian calendar for example numbers its years in the Western Anno Domini system (the Coptic Orthodox and Ethiopian Orthodox churches have their own Christian eras). The instant, date, or year from which time is marked is called the epoch of the era. There are many different calendar eras such as Saka Era.
| Gregorian calendar | 2023 MMXXIII |
| Ab urbe condita | 2776 |
| Armenian calendar | 1472 ԹՎ ՌՆՀԲ |
| Assyrian calendar | 6773 |
| Bahá'í calendar | 179–180 |
| Balinese saka calendar | 1944–1945 |
| Bengali calendar | 1430 |
| Berber calendar | 2973 |
| British Regnal year | 71 Eliz. 2 – 72 Eliz. 2 |
| Buddhist calendar | 2567 |
| Burmese calendar | 1385 |
| Byzantine calendar | 7531–7532 |
| Chinese calendar | 壬寅年 (Water Tiger) 4719 or 4659 — to — 癸卯年 (Water Rabbit) 4720 or 4660 |
| Coptic calendar | 1739–1740 |
| Discordian calendar | 3189 |
| Ethiopian calendar | 2015–2016 |
| Hebrew calendar | 5783–5784 |
| Hindu calendars | |
| - Vikram Samvat | 2079–2080 |
| - Shaka Samvat | 1944–1945 |
| - Kali Yuga | 5123–5124 |
| Holocene calendar | 12023 |
| Igbo calendar | 1023–1024 |
| Iranian calendar | 1401–1402 |
| Islamic calendar | 1444–1445 |
| Japanese calendar | Reiwa 5 (令和５年) |
| Javanese calendar | 1956–1957 |
| Juche calendar | 112 |
| Julian calendar | Gregorian minus 13 days |
| Korean calendar | 4356 |
| Minguo calendar | ROC 112 民國112年 |
| Nanakshahi calendar | 555 |
| Thai solar calendar | 2566 |
| Tibetan calendar | 阳水虎年 (male Water-Tiger) 2149 or 1768 or 996 — to — 阴水兔年 (female Water-Rabbit) 2150 or 1769 or 997 |
| Unix time | 1672531200 – 1704067199 |
In ancient times, regnal years were counted from the year a new monarch took the throne. This makes ancient timelines very difficult to reconstruct, because they are based on separate and scattered king lists, such as the Sumerian King List and the Babylonian Canon of Kings. In East Asia, having era names based on ruling monarchs ended in the 20th century except for Japan, where they are still used.