| Millennium: | 1st millennium |
|---|---|
| Centuries: | 4th century – 5th century – 6th century |
| Decades: | 370s 380s 390s – 400s – 410s 420s 430s |
| Years: | 400 401 402 – 403 – 404 405 406 |
| 403 by topic | |
| Politics | |
| State leaders – Sovereign states | |
| Birth and death categories | |
| Births – Deaths | |
| Establishment and disestablishment categories | |
| Establishments – Disestablishments | |
| Gregorian calendar | 403 CDIII |
| Ab urbe condita | 1156 |
| Armenian calendar | N/A |
| Assyrian calendar | 5153 |
| Bahá'í calendar | -1441–-1440 |
| Bengali calendar | -190 |
| Berber calendar | 1353 |
| English Regnal year | N/A |
| Buddhist calendar | 947 |
| Burmese calendar | -235 |
| Byzantine calendar | 5911–5912 |
| Chinese calendar | 壬寅年十一月廿二日 (3039/3099-11-22) — to —
癸卯年十二月初二日(3040/3100-12-2) |
| Coptic calendar | 119–120 |
| Ethiopian calendar | 395–396 |
| Hebrew calendar | 4163–4164 |
| Hindu calendars | |
| - Vikram Samvat | 459–460 |
| - Shaka Samvat | 325–326 |
| - Kali Yuga | 3504–3505 |
| Holocene calendar | 10403 |
| Iranian calendar | 219 BP – 218 BP |
| Islamic calendar | 226 BH – 225 BH |
| Japanese calendar | |
| Korean calendar | 2736 |
| Minguo calendar | 1509 before ROC 民前1509年 |
| Thai solar calendar | 946 |
Year 403 (CDIII) was a common year starting on Thursday (link will display the full calendar) of the Julian calendar. At the time, it was known as the Year of the Consulship of Theodosius and Rumoridus (or, less frequently, year 1156 Ab urbe condita). The denomination 403 for this year has been used since the early medieval period, when the Anno Domini calendar era became the prevalent method in Europe for naming years.