| Millennium: | 1st millennium |
|---|---|
| Centuries: | |
| Decades: | |
| Years: |
| AD 666 by topic |
|---|
| Leaders |
| Categories |
| Gregorian calendar | 666 DCLXVI |
| Ab urbe condita | 1419 |
| Armenian calendar | 115 ԹՎ ՃԺԵ |
| Assyrian calendar | 5416 |
| Balinese saka calendar | 587–588 |
| Bengali calendar | 73 |
| Berber calendar | 1616 |
| Buddhist calendar | 1210 |
| Burmese calendar | 28 |
| Byzantine calendar | 6174–6175 |
| Chinese calendar | 乙丑年 (Wood Ox) 3363 or 3156 — to — 丙寅年 (Fire Tiger) 3364 or 3157 |
| Coptic calendar | 382–383 |
| Discordian calendar | 1832 |
| Ethiopian calendar | 658–659 |
| Hebrew calendar | 4426–4427 |
| Hindu calendars | |
| - Vikram Samvat | 722–723 |
| - Shaka Samvat | 587–588 |
| - Kali Yuga | 3766–3767 |
| Holocene calendar | 10666 |
| Iranian calendar | 44–45 |
| Islamic calendar | 45–46 |
| Japanese calendar | Hakuchi 17 (白雉１７年) |
| Javanese calendar | 557–558 |
| Julian calendar | 666 DCLXVI |
| Korean calendar | 2999 |
| Minguo calendar | 1246 before ROC 民前1246年 |
| Nanakshahi calendar | −802 |
| Seleucid era | 977/978 AG |
| Thai solar calendar | 1208–1209 |
| Tibetan calendar | 阴木牛年 (female Wood-Ox) 792 or 411 or −361 — to — 阳火虎年 (male Fire-Tiger) 793 or 412 or −360 |
Year 666 (DCLXVI) was a common year starting on Thursday (link will display the full calendar) of the Julian calendar. The denomination 666 for this year has been used since the early medieval period, when the Anno Domini calendar era became the prevalent method in Europe for naming years.