Everything I knew about fox and coyote hunting has seemed to go out the window the past few years. Numbers have been way down (seems like they're making a comeback though) and it really seems like every one that is out there is completely call shy. In the last 5 years I've gotten every one of my fox or yotes from just seeing them as I'm driving from one place to another. But I have spent minimal time calling so that's not the best statement. But anyway, back to the point. When hunting was good, we could call them in almost any time of day. We'd go out about an hour before sunrise and howl. If we got replies (and nearly always did) we would come back and call there during light hours. There's many things that affect fox that could keep you from seeing anything all day. I'm far from an expert but I'd say don't be discouraged to try any time during the day. Mornings "should" be the most active time and it's been morning when I've seen the most action, but certainly not the only time.