| Millennium: | 1st millennium |
|---|---|
| Centuries: | 2nd century – 3rd century – 4th century |
| Decades: | 210s 220s 230s – 240s – 250s 260s 270s |
| Years: | 237 238 239 – 240 – 241 242 243 |
| 240 by topic | |
| Politics | |
| State leaders – Sovereign states | |
| Birth and death categories | |
| Births – Deaths | |
| Establishment and disestablishment categories | |
| Establishments – Disestablishments | |
| Gregorian calendar | 240 CCXL |
| Ab urbe condita | 993 |
| Armenian calendar | N/A |
| Bahá'í calendar | -1604 – -1603 |
| Bengali calendar | -353 |
| Berber calendar | 1190 |
| Buddhist calendar | 784 |
| Burmese calendar | -398 |
| Byzantine calendar | 5748 – 5749 |
| Chinese calendar | 己未年十二月二十日 (2876/2936-12-20) — to —
庚申年十二月初一日(2877/2937-12-1) |
| Coptic calendar | -44 – -43 |
| Ethiopian calendar | 232 – 233 |
| Hebrew calendar | 4000 – 4001 |
| Hindu calendars | |
| - Bikram Samwat | 296 – 297 |
| - Shaka Samvat | 162 – 163 |
| - Kali Yuga | 3341 – 3342 |
| Holocene calendar | 10240 |
| Iranian calendar | 382 BP – 381 BP |
| Islamic calendar | 394 BH – 393 BH |
| Japanese calendar | |
| Korean calendar | 2573 |
| Thai solar calendar | 783 |