The category is for articles and events specifically related to the decade of the 1400s which begins in the year 1400 and ends in the year 1409.
Note that 1400 is actually the last year of the 14th century; 1401 is the actual first year of the 15th century.
Wikimedia Commons has media related to 1400s
This category has the following 12 subcategories, out of 12 total.
Pages in category "1400s"
The following 2 pages are in this category, out of 2 total.