2 books with great advices about how to handle Time Travel in TTRPG :
"Gurps time travel"
http://www.sjgames.com/gurps/books/timetravel/
Available
"All Our Yesterdays: The Time Travel Sourcebook"
https://www.rpg.net/reviews/archive/...rev_3610.phtml
Hard to find. Most of it is Star Trek based, but there is a chapter on narrating Time Travel adventures that I found useful.