| Centuries: | 3rd century · 4th century · 5th century |
| Decades: | 360s 370s 380s 390s 400s 410s 420s |
| Years: | 396 397 398 399 400 401 402 |
| 399 by topic | |
| Politics | |
| State leaders – Sovereign states | |
| Birth and death categories | |
| Births – Deaths | |
| Establishment and disestablishment categories | |
| Establishments – Disestablishments | |
| Gregorian calendar | 399 CCCXCIX |
| Ab urbe condita | 1152 |
| Armenian calendar | N/A |
| Bahá'í calendar | -1445 – -1444 |
| Bengali calendar | -194 |
| Berber calendar | 1349 |
| Buddhist calendar | 943 |
| Burmese calendar | -239 |
| Byzantine calendar | 5907 – 5908 |
| Chinese calendar | 戊戌年閏十一月初八日 (3035/3095-intercalary 11-8) — to —
己亥年十一月十八日(3036/3096-11-18) |
| Coptic calendar | 115 – 116 |
| Ethiopian calendar | 391 – 392 |
| Hebrew calendar | 4159 – 4160 |
| Hindu calendars | |
| - Bikram Samwat | 455 – 456 |
| - Shaka Samvat | 321 – 322 |
| - Kali Yuga | 3500 – 3501 |
| Holocene calendar | 10399 |
| Iranian calendar | 223 BP – 222 BP |
| Islamic calendar | 230 BH – 229 BH |
| Japanese calendar | |
| Korean calendar | 2732 |
| Thai solar calendar | 942 |