| Centuries: | 4th century · 5th century · 6th century |
| Decades: | 390s 400s 410s 420s 430s 440s 450s |
| Years: | 420 421 422 423 424 425 426 |
| 423 by topic | |
| Politics | |
| State leaders – Sovereign states | |
| Birth and death categories | |
| Births – Deaths | |
| Establishment and disestablishment categories | |
| Establishments – Disestablishments | |
| Gregorian calendar | 423 CDXXIII |
| Ab urbe condita | 1176 |
| Armenian calendar | N/A |
| Bahá'í calendar | -1421 – -1420 |
| Bengali calendar | -170 |
| Berber calendar | 1373 |
| Buddhist calendar | 967 |
| Burmese calendar | -215 |
| Byzantine calendar | 5931 – 5932 |
| Chinese calendar | 壬戌年十二月初四日 (3059/3119-12-4) — to —
癸亥年十一月十三日(3060/3120-11-13) |
| Coptic calendar | 139 – 140 |
| Ethiopian calendar | 415 – 416 |
| Hebrew calendar | 4183 – 4184 |
| Hindu calendars | |
| - Bikram Samwat | 479 – 480 |
| - Shaka Samvat | 345 – 346 |
| - Kali Yuga | 3524 – 3525 |
| Holocene calendar | 10423 |
| Iranian calendar | 199 BP – 198 BP |
| Islamic calendar | 205 BH – 204 BH |
| Japanese calendar | |
| Korean calendar | 2756 |
| Thai solar calendar | 966 |