Depending on what your using, I got (since I'm mobile) mt_rand being 300,000 ms faster running a few iterations in just a little for loop. Regardless of what you would use here I don't think it really matters as Guest stated. But what I would do for a module like this is store the next time the module should become available, give the players a little window like 2 hours and let the module do it's thing.
You can use something like a string for the date so it's human readable or just a timestamp, and using getdate() may be pretty simple to manipulate visually in your code of what you want or use time() and do some fancy math like time()+ (2*60*60) to get 2 hours ahead or reverse to get 2 hours before and see if your current timestamp falls within your allowance.