The way your Canvas time zone is supposed to work is that if you don’t set a time zone in your individual account, then it should automatically default to the default time zone that we have set globally to Mountain Standard Time (MST-AZ).
If you set a time zone in your account, however, then that individual setting trumps the default.
Here’s the instructions on how to set their time zone (if needed):
https://community.instructure.com/en/kb/articles/662896-how-do-i-set-a-time-zone-in-my-user-account