| Centuries: | 6th century · 7th century · 8th century |
| Decades: | 610s 620s 630s 640s 650s 660s 670s |
| Years: | 640 641 642 643 644 645 646 |
| 643 by topic | |
| Politics | |
| State leaders – Sovereign states | |
| Birth and death categories | |
| Births – Deaths | |
| Establishment and disestablishment categories | |
| Establishments – Disestablishments | |
| Gregorian calendar | 643 DCXLIII |
| Ab urbe condita | 1396 |
| Armenian calendar | 92 ԹՎ ՂԲ |
| Bahá'í calendar | -1201 – -1200 |
| Bengali calendar | 50 |
| Berber calendar | 1593 |
| Buddhist calendar | 1187 |
| Burmese calendar | 5 |
| Byzantine calendar | 6151 – 6152 |
| Chinese calendar | 壬寅年十二月初六日 (3279/3339-12-6) — to —
癸卯年十一月十五日(3280/3340-11-15) |
| Coptic calendar | 359 – 360 |
| Ethiopian calendar | 635 – 636 |
| Hebrew calendar | 4403 – 4404 |
| Hindu calendars | |
| - Bikram Samwat | 699 – 700 |
| - Shaka Samvat | 565 – 566 |
| - Kali Yuga | 3744 – 3745 |
| Holocene calendar | 10643 |
| Iranian calendar | 21 – 22 |
| Islamic calendar | 22 – 23 |
| Japanese calendar | |
| Korean calendar | 2976 |
| Thai solar calendar | 1186 |