TT is safe if you do it the right way ;-)
In my experience - I TT a lot - you have to be aware of this: don't TT into the future, no benefits from that. If you do it to claim more from the awards, you screw up the timer and it takes a lot of work to get it right - done that, was not funny. Next: If you play on iOS, you have to close the game completely between changing the date, it won't work otherwise. Next: When you TT into the past, you have to return one day after the other, if you jump ahead to the present, you lose your progress with the Angel-Talisman. I use TT particularly to restore energy and strength, to get the Angel-Talisman faster or to do my complete gifting - with more than 60 friends you you either leave some of them without gift or you TT to gift everybody in you friendslist. I prefer the latter. Be aware that these are my own experiences on MacOS. It may differ from iOS, but my sister plays on iOS and we did it on her machine and it worked.