Looking at it, the value of the text box next to the Starting Time changes, but since we don't know which option in the menu relates to which TZ and plus the fact that some TZs are doubled up, I propose the following. Change the Starting Time Hour to a non zero value, then change the time zone and then use utils.wait.wait_for to wait until the Hour is reset back to 0. It's a little hacky, but in the absence of any other visible changes, I can't see much else we can do.