| Centuries: | 6th century · 7th century · 8th century |
| Decades: | 630s 640s 650s 660s 670s 680s 690s |
| Years: | 665 666 667 668 669 670 671 |
| 668 by topic | |
| Politics | |
| State leaders – Sovereign states | |
| Birth and death categories | |
| Births – Deaths | |
| Establishment and disestablishment categories | |
| Establishments – Disestablishments | |
| Gregorian calendar | 668 DCLXVIII |
| Ab urbe condita | 1421 |
| Armenian calendar | 117 ԹՎ ՃԺԷ |
| Bahá'í calendar | -1176 – -1175 |
| Bengali calendar | 75 |
| Berber calendar | 1618 |
| Buddhist calendar | 1212 |
| Burmese calendar | 30 |
| Byzantine calendar | 6176 – 6177 |
| Chinese calendar | 丁卯年十二月十二日 (3304/3364-12-12) — to —
戊辰年十一月廿三日(3305/3365-11-23) |
| Coptic calendar | 384 – 385 |
| Ethiopian calendar | 660 – 661 |
| Hebrew calendar | 4428 – 4429 |
| Hindu calendars | |
| - Bikram Samwat | 724 – 725 |
| - Shaka Samvat | 590 – 591 |
| - Kali Yuga | 3769 – 3770 |
| Holocene calendar | 10668 |
| Iranian calendar | 46 – 47 |
| Islamic calendar | 47 – 48 |
| Japanese calendar | |
| Korean calendar | 3001 |
| Thai solar calendar | 1211 |