Actually, time travel is confusing on many levels—what the hell did happen in Twelve Monkeys exactly?—but it’s the simple things that can cause the biggest headaches. Especially, as the mouse-over text in XKCD points out, the countdown: “T-minus 10… 11…”. [XKCD]
https://gizmodo.com/a-flow-chart-explaining-all-time-travel-in-movies-5994682