I would try an hour or two before dusk if you can, see how they do with that for a few days or a week, and if all is going well and you want to give them more time, let them out earlier. you'll find a schedule that works for you.
mine are out, in a fenced yard all day from dawn to dusk and they love it. I was afraid they wouldn't go back in at night and I be chasing chickens around the yard on a nightly basis, but from day 1 they head in as soon as the sun falls over the horizon, like clockwork. so don't worry about them not going in at night, they will.
one thing I will say though, chickens hop fences!
I have 4 ft. chain-link fencing and they all(some breeds more than others) have jumped the fence. the problem, I have neighbor dogs on all 3 sides that would LOVE to "play" with a chicken. I'm home all day though, so every time one of them has jumped, I go after them. I'm hoping
that they've learned that nothing good comes from jumping the fence because they haven't done it much at all lately. so keep in mind that chickens DO fly. even with clipped wings(I clipped all mine, didn't phase em a bit)