| Centuries: | 4th century · 5th century · 6th century |
| Decades: | 370s 380s 390s 400s 410s 420s 430s |
| Years: | 398 399 400 401 402 403 404 |
| 401 by topic | |
| Politics | |
| State leaders – Sovereign states | |
| Birth and death categories | |
| Births – Deaths | |
| Establishment and disestablishment categories | |
| Establishments – Disestablishments | |
| Gregorian calendar | 401 CDI |
| Ab urbe condita | 1154 |
| Armenian calendar | N/A |
| Bahá'í calendar | -1443 – -1442 |
| Bengali calendar | -192 |
| Berber calendar | 1351 |
| Buddhist calendar | 945 |
| Burmese calendar | -237 |
| Byzantine calendar | 5909 – 5910 |
| Chinese calendar | 庚子年十二月初一日 (3037/3097-12-1) — to —
辛丑年十一月十一日(3038/3098-11-11) |
| Coptic calendar | 117 – 118 |
| Ethiopian calendar | 393 – 394 |
| Hebrew calendar | 4161 – 4162 |
| Hindu calendars | |
| - Bikram Samwat | 457 – 458 |
| - Shaka Samvat | 323 – 324 |
| - Kali Yuga | 3502 – 3503 |
| Holocene calendar | 10401 |
| Iranian calendar | 221 BP – 220 BP |
| Islamic calendar | 228 BH – 227 BH |
| Japanese calendar | |
| Korean calendar | 2734 |
| Thai solar calendar | 944 |