840s ke ngwagasome tšhupamabakeng ya Gregorian wa go thoma ka 1 Pherekgong 840 ya fela ka 31 Manthole 849. Ngwagasome 840s o wela ngwagengkgolo wa 9.
| Ngwagakete: | Ngwagakete1 |
| Mengwagakgolo: | Ngwagakgolo 8 – Ngwagakgolo 9 – Ngwagakgolo 10 |
| Mengwagasome: | 810s 820s 830s – 840s – 850s 860s 870s |
| Mengwaga: | 840 841 842 843 844 845 846 847 848 849 |
| 840s-tšago tswalanya: |