Tor won't work unless you have an accurate clock, because clients measure how long it takes to build circuits and they will fail to build them if it takes 5 hours or -5 hours, for example. That being said, all Tor clients use UTC and Tails should update the time when it starts, so changing your time zone won't affect that. However, if you set it to some weird time zone that hardly anybody lives in, like in the middle of the Pacific Ocean, and you use a protocol that leaks time zone, like XMPP, then that can be bad for your anonymity, otherwise it's not a problem.