640s
640s ke ngwagasome tšhupamabakeng ya Gregorian wa go thoma ka 1 Pherekgong 640 ya fela ka 31 Manthole 649. Ngwagasome 640s o wela ngwagengkgolo wa 7.
| Ngwagakete: | Ngwagakete 1 |
| Mengwagakgolo: | Ngwagakgolo 6 – Ngwagakgolo 7 – Ngwagakgolo 8 |
| Mengwagasome: | 610s 620s 630s – 640s – 650s 660s 670s |
| Mengwaga: | 640 641 642 643 644 645 646 647 648 649 |
| 640s-tšago tswalanya: |