Ok, do this:
Make a trigge rthat, when a unit dies it runs a for int a = 30, statement and each time it checks if its night-time. If it is night-time it revives the unit and "exits" the trigger. If it doesn't find that its night-time it runs again.
Make the for statemnt run, the amount of time (in seconds) it takes for it to switch between night-time and daytime, /10