There already exists a fantastic timer that can be implemented in-game, and I'm sure it could probably be configured to set to spawn times. Personally, I don't use it, so I can't tell you it can do so with an absolute, 100% certainty to my words...I'm fairly certain it can, though, by setting up a blank timer for a given amount of time.
You can find and configure
Arista's UI TimerMod HERE. I hope this is what you're looking for...or at least close.
Ameril Dan`nodel
Warder, 57th season
[
Lanys T`Vyl server ]
Bitch at Amiez!! -- in the words of Spleen.