Why hasn't he called yet? ?

Hmmm... Well like others are saying, it's only been a day so you should probably wait another day or two. See, guys don't want to come off as desperate so they don't call you within a day. If they do call you within 24 hours, they are desperate and you should not put up with that. You should always avoid a desperate guy. And just for your sake, if a guy gives you his number, do not call within 24 hours because you will look desperate too. He could also not be calling you because he does have a girlfriend and he doesn't want to cheat. So in conclusion, if he doesn't call in the next three days, he is not interested.