Timed Light that turns ON every 30 minutes, press button to turn off
Easy peasy.  

Get a common, mains-rated 30-minute rundown timer - the kind of thing you see on bathroom fans or heat lamps.   

Except look for a special version of this which is either "Normally Closed", "NC" or "SPDT".  You might have to hit up Galco or Grainger for this.  

If you get the kind that is mechanical, it wires up like a plain old light switch. And that's exactly what you do; you wire up the switch and light exactly like a light switch circuit.    

If you wire it as a "switch loop", I'll admonish you to obey NEC 2011 and provide a neutral wire.  (I.e. Use /3 cable in the switch loop). That is because there are many other ways to solve this problem, and almost all of them will call for a powered device that will require neutral.