| Millennium: | 1st millennium |
|---|---|
| Centuries: | 1st century BC – 1st century – 2nd century |
| Decades: | 10s 20s 30s – 40s – 50s 60s 70s |
| Years: | 37 38 39 – 40 – 41 42 43 |
| 40 by topic | |
| Politics | |
| State leaders – Sovereign states | |
| Birth and death categories | |
| Births – Deaths | |
| Establishment and disestablishment categories | |
| Establishments – Disestablishments | |
| Gregorian calendar | 40 XL |
| Ab urbe condita | 793 |
| Armenian calendar | N/A |
| Bahá'í calendar | -1804 – -1803 |
| Bengali calendar | -553 |
| Berber calendar | 990 |
| Buddhist calendar | 584 |
| Burmese calendar | -598 |
| Byzantine calendar | 5548 – 5549 |
| Chinese calendar | 己亥年十一月廿八日 (2676/2736-11-28) — to —
庚子年十一月初九日(2677/2737-11-9) |
| Coptic calendar | -244 – -243 |
| Ethiopian calendar | 32 – 33 |
| Hebrew calendar | 3800 – 3801 |
| Hindu calendars | |
| - Bikram Samwat | 96 – 97 |
| - Shaka Samvat | N/A |
| - Kali Yuga | 3141 – 3142 |
| Holocene calendar | 10040 |
| Iranian calendar | 582 BP – 581 BP |
| Islamic calendar | 600 BH – 599 BH |
| Japanese calendar | |
| Korean calendar | 2373 |
| Thai solar calendar | 583 |
Year 40 (XL) was a leap year starting on Friday (link will display the full calendar) of the Julian calendar.