all the advice lists i ever saw about running a d&d campaign always explicitly told you not to run time travel. being the kind of DM i am i saw that as more of a challenge than anything.

turns out they were right. every time a time loop or the present was contradicted because of how freeform d&d is i either had to patch it up, or... introduce another time loop. by the end i had 5 time loops, some recursive, and my players had completely lost track.

don't do time travel in d&d