Year 400 (CD) was a leap year starting on Sunday (link will display the full calendar) of the Julian calendar. In the Roman Empire, it was known as the Year of the Consulship of Stilicho and Aurelianus (or, less frequently, year 1153 Ab urbe condita). The denomination 400 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.
|Centuries:||3rd century – 4th century – 5th century|
|Decades:||370s 380s 390s – 400s – 410s 420s 430s|
|Years:||397 398 399 – 400 – 401 402 403|
- First invasion of Italy by Alaric (probable date).
- The Vandals start their westward trek from Dacia and Hungary (approximate date).
- Construction (and therefore occupation) at Great Zimbabwe begins (approximate date).
- Earliest date of human occupation on Easter Island (approximate date).
- Chrysanthemums are introduced to Japan (approximate date).