The time line Andrew drew on the wall was actually drawn on a roll of photographer's background paper and hung on the wall.
When shooting wrapped for the scenes featuring the time line, it was almost thrown out. A last minute change of heart saved the time line, which proved fortunate as some of those scenes were later re-shot.
Due to a last minute script change, the A.D. had to play the role of the Assassin working for the Anti-Christ when there was no time to audition an actor for the role.