| Centuries: | 3rd century · 4th century · 5th century |
| Decades: | 310s 320s 330s 340s 350s 360s 370s |
| Years: | 337 338 339 340 341 342 343 |
| 340 by topic | |
| Politics | |
| State leaders – Sovereign states | |
| Birth and death categories | |
| Births – Deaths | |
| Establishment and disestablishment categories | |
| Establishments – Disestablishments | |
| Gregorian calendar | 340 CCCXL |
| Ab urbe condita | 1093 |
| Armenian calendar | N/A |
| Bahá'í calendar | -1504 – -1503 |
| Bengali calendar | -253 |
| Berber calendar | 1290 |
| Buddhist calendar | 884 |
| Burmese calendar | -298 |
| Byzantine calendar | 5848 – 5849 |
| Chinese calendar | 己亥年十一月十六日 (2976/3036-11-16) — to —
庚子年十一月廿六日(2977/3037-11-26) |
| Coptic calendar | 56 – 57 |
| Ethiopian calendar | 332 – 333 |
| Hebrew calendar | 4100 – 4101 |
| Hindu calendars | |
| - Bikram Samwat | 396 – 397 |
| - Shaka Samvat | 262 – 263 |
| - Kali Yuga | 3441 – 3442 |
| Holocene calendar | 10340 |
| Iranian calendar | 282 BP – 281 BP |
| Islamic calendar | 291 BH – 290 BH |
| Japanese calendar | |
| Korean calendar | 2673 |
| Thai solar calendar | 883 |