In that case, you'll want to use something like cron.

Woodchuck doesn't care about the particular time that something occurs; Woodchuck cares about the conditions in which it occurs. So, if you happen to plug in your phone and have WiFi at noon, it may trigger an update when the phone becomes idle. That's better, I think, than updating over cellular at 23:00, because you happen to be at the bar instead of at home, as you usually are.