| Millennium: | 1st millennium |
|---|---|
| Centuries: | 1st century BC – 1st century – 2nd century |
| Decades: | 0s 10s 20s – 30s – 40s 50s 60s |
| Years: | 28 29 30 – 31 – 32 33 34 |
| 31 by topic | |
| Politics | |
| State leaders – Sovereign states | |
| Birth and death categories | |
| Births – Deaths | |
| Establishment and disestablishment categories | |
| Establishments – Disestablishments | |
| Gregorian calendar | 31 XXXI |
| Ab urbe condita | 784 |
| Armenian calendar | N/A |
| Bahá'í calendar | -1813 – -1812 |
| Bengali calendar | -562 |
| Berber calendar | 981 |
| Buddhist calendar | 575 |
| Burmese calendar | -607 |
| Byzantine calendar | 5539 – 5540 |
| Chinese calendar | 庚寅年十一月十九日 (2667/2727-11-19) — to —
辛卯年十一月廿八日(2668/2728-11-28) |
| Coptic calendar | -253 – -252 |
| Ethiopian calendar | 23 – 24 |
| Hebrew calendar | 3791 – 3792 |
| Hindu calendars | |
| - Bikram Samwat | 87 – 88 |
| - Shaka Samvat | N/A |
| - Kali Yuga | 3132 – 3133 |
| Holocene calendar | 10031 |
| Iranian calendar | 591 BP – 590 BP |
| Islamic calendar | 609 BH – 608 BH |
| Japanese calendar | |
| Korean calendar | 2364 |
| Thai solar calendar | 574 |
Year 31 (XXXI) was a common year starting on Monday (link will display the full calendar) of the Julian calendar.