What Happened in 1203
- T 1
- W 2
- T 3
- F 4
- S 5
- S 6
- M 7
- T 8
- W 9
- T 10
- F 11
- S 12
- S 13
- M 14
- T 15
- W 16
- T 17
- F 18
- S 19
- S 20
- M 21
- T 22
- W 23
- T 24
- F 25
- S 26
- S 27
- M 28
- T 29
- W 30
- T 31
- Jul 17 Siege of Constantinople begins during the fourth Crusade; Roman Catholic Crusaders aboard a Venetian fleet attack the city
- Aug 1 Alexius IV Angelus appointed co-regent of Byzantium
- Nov 4 Dirk VII, Count of Holland (1190-1203), dies