Mine crow all day long and some really enjoy crowing right in my ear when I'm standing outside with them. lol Last night we went out in the dark to swap some birds around into breeding pens and there was a roo crowing. I don't think it matters time of day..or light or dark. It is pretty much whenever they feel like letting one out.
I sometimes think that it depends on the age and breed of the roo. We've had some that started crowing at 8 weeks, loved the sounds of their own voices and kept it up. Our other little guy (we suspected but weren't sure he was a roo) kept himself quiet up until 2 weeks ago. Crowed once, then stopped. 3 weeks later, he's now crowing in the morning about every 4-5 days, as he feels led and now he just crowed in the middle of the day about 12 times.
I had a Silkie roo and he was kind of quiet. Then when he started to crow he sounded like a boy whose voice was changing, sort of like a frog croaking. When he finally started making noise, it seemed to be whenever he felt like it. Definitely, no later than 5:30 in the morning. Best darn alarm clock I ever had, but no fun when I didn't have to go to work!
Mine crows WHENEVER he feels like it. He also greets anyone who pulls into the driveway and says by when they leave. When I am holding him he crows and talks to me. The first time he crowed when I was holding him I almost dropped him lol. He isn't even angry when he does it.