Back 1666 Abkhazian 1666 Afrikaans 1666 ALS 1666 እ.ኤ.አ. Amharic 1666 AN 1666 Arabic 1666 ARZ 1666 AST 1666 AVK 1666 Azerbaijani
| Millennium: | 2nd millennium |
|---|---|
| Centuries: | 16th century – 17th century – 18th century |
| Decades: | 1630s 1640s 1650s – 1660s – 1670s 1680s 1690s |
| Years: | 1663 1664 1665 – 1666 – 1667 1668 1669 |
| Gregorian calendar | 1666 MDCLXVI |
| Ab urbe condita | 2419 |
| Armenian calendar | 1115 ԹՎ ՌՃԺԵ |
| Assyrian calendar | 6416 |
| Balinese saka calendar | 1587–1588 |
| Bengali calendar | 1073 |
| Berber calendar | 2616 |
| English Regnal year | 17 Cha. 2 – 18 Cha. 2 |
| Buddhist calendar | 2210 |
| Burmese calendar | 1028 |
| Byzantine calendar | 7174–7175 |
| Chinese calendar | 乙巳年 (Wood Snake) 4362 or 4302 — to — 丙午年 (Fire Horse) 4363 or 4303 |
| Coptic calendar | 1382–1383 |
| Discordian calendar | 2832 |
| Ethiopian calendar | 1658–1659 |
| Hebrew calendar | 5426–5427 |
| Hindu calendars | |
| - Vikram Samvat | 1722–1723 |
| - Shaka Samvat | 1587–1588 |
| - Kali Yuga | 4766–4767 |
| Holocene calendar | 11666 |
| Igbo calendar | 666–667 |
| Iranian calendar | 1044–1045 |
| Islamic calendar | 1076–1077 |
| Japanese calendar | Kanbun 5 (寛文５年) |
| Javanese calendar | 1588–1589 |
| Julian calendar | Gregorian minus 10 days |
| Korean calendar | 3999 |
| Minguo calendar | 246 before ROC 民前246年 |
| Nanakshahi calendar | 198 |
| Thai solar calendar | 2208–2209 |
| Tibetan calendar | 阴木蛇年 (female Wood-Snake) 1792 or 1411 or 639 — to — 阳火马年 (male Fire-Horse) 1793 or 1412 or 640 |
1666 (MDCLXVI) was a common year starting on Friday of the Gregorian calendar and a common year starting on Monday of the Julian calendar, the 1666th year of the Common Era (CE) and Anno Domini (AD) designations, the 666th year of the 2nd millennium, the 66th year of the 17th century, and the 7th year of the 1660s decade. As of the start of 1666, the Gregorian calendar was 10 days ahead of the Julian calendar, which remained in localized use until 1923.