| Centuries: | 4th century · 5th century · 6th century |
| Decades: | 390s 400s 410s 420s 430s 440s 450s |
| Years: | 417 418 419 420 421 422 423 |
| 420 by topic | |
| Politics | |
| State leaders – Sovereign states | |
| Birth and death categories | |
| Births – Deaths | |
| Establishment and disestablishment categories | |
| Establishments – Disestablishments | |
| Gregorian calendar | 420 CDXX |
| Ab urbe condita | 1173 |
| Armenian calendar | N/A |
| Bahá'í calendar | -1424 – -1423 |
| Bengali calendar | -173 |
| Berber calendar | 1370 |
| Buddhist calendar | 964 |
| Burmese calendar | -218 |
| Byzantine calendar | 5928 – 5929 |
| Chinese calendar | 己未年十一月三十日 (3056/3116-11-30) — to —
庚申年十一月十一日(3057/3117-11-11) |
| Coptic calendar | 136 – 137 |
| Ethiopian calendar | 412 – 413 |
| Hebrew calendar | 4180 – 4181 |
| Hindu calendars | |
| - Bikram Samwat | 476 – 477 |
| - Shaka Samvat | 342 – 343 |
| - Kali Yuga | 3521 – 3522 |
| Holocene calendar | 10420 |
| Iranian calendar | 202 BP – 201 BP |
| Islamic calendar | 208 BH – 207 BH |
| Japanese calendar | |
| Korean calendar | 2753 |
| Thai solar calendar | 963 |