Changing a screen's timezone applies to scheduled content right away

Correcting a screen’s timezone had no effect on what it played. Scheduled content kept following the old timezone until the player happened to restart, so a screen set up in the wrong timezone could run a breakfast menu at lunchtime with nothing on the screen to explain why.

A timezone change now applies within about half a second. Set the timezone on a screen that has been running for weeks, and the next scheduled item is the right one.