The 400s was a decade that started on 1 January 400 and ended on 31 December 409.

Millennium: 1st millennium
Centuries: 4th century5th century6th century
Decades: 370s 380s 390s400s410s 420s 430s
Years: 400 401 402 403 404 405 406 407 408 409
Categories: BirthsDeathsArchitecture
EstablishmentsDisestablishments

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