| Millennium: | 2nd millennium |
|---|---|
| Centuries: | |
| Decades: | |
| Years: |
| 1866 by topic |
|---|
| Humanities |
| By country |
| Other topics |
| Lists of leaders |
| Birth and death categories |
| Establishments and disestablishments categories |
| Works category |
| Gregorian calendar | 1866 MDCCCLXVI |
| Ab urbe condita | 2619 |
| Armenian calendar | 1315 ԹՎ ՌՅԺԵ |
| Assyrian calendar | 6616 |
| Baháʼí calendar | 22–23 |
| Balinese saka calendar | 1787–1788 |
| Bengali calendar | 1273 |
| Berber calendar | 2816 |
| British Regnal year | 29 Vict. 1 – 30 Vict. 1 |
| Buddhist calendar | 2410 |
| Burmese calendar | 1228 |
| Byzantine calendar | 7374–7375 |
| Chinese calendar | 乙丑年 (Wood Ox) 4563 or 4356 — to — 丙寅年 (Fire Tiger) 4564 or 4357 |
| Coptic calendar | 1582–1583 |
| Discordian calendar | 3032 |
| Ethiopian calendar | 1858–1859 |
| Hebrew calendar | 5626–5627 |
| Hindu calendars | |
| - Vikram Samvat | 1922–1923 |
| - Shaka Samvat | 1787–1788 |
| - Kali Yuga | 4966–4967 |
| Holocene calendar | 11866 |
| Igbo calendar | 866–867 |
| Iranian calendar | 1244–1245 |
| Islamic calendar | 1282–1283 |
| Japanese calendar | Keiō 2 (慶応２年) |
| Javanese calendar | 1794–1795 |
| Julian calendar | Gregorian minus 12 days |
| Korean calendar | 4199 |
| Minguo calendar | 46 before ROC 民前46年 |
| Nanakshahi calendar | 398 |
| Thai solar calendar | 2408–2409 |
| Tibetan calendar | 阴木牛年 (female Wood-Ox) 1992 or 1611 or 839 — to — 阳火虎年 (male Fire-Tiger) 1993 or 1612 or 840 |
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1866 (MDCCCLXVI) was a common year starting on Monday of the Gregorian calendar and a common year starting on Saturday of the Julian calendar, the 1866th year of the Common Era (CE) and Anno Domini (AD) designations, the 866th year of the 2nd millennium, the 66th year of the 19th century, and the 7th year of the 1860s decade. As of the start of 1866, the Gregorian calendar was 12 days ahead of the Julian calendar, which remained in localized use until 1923.