First of all, I do not commute to work. Being retired I have a bit more time flexibility than many.
I do though ride all year and use the bike for errands and getting to meetings etc.
When possible I want to ride between 10:00AM and 3:00PM. Then I like to ride between 6:30PM and Ten PM.
School and work traffic is generally gone by ten AM. The fog may have also lifted by then. At around 3PM school lets out and kids are connecting with one another on cell phones. As we approach five PM more adults are also on the phone and traffic is increasing.
I live in a small town and my side streets get me to a bike trail that heads into the downtown area. Night riding is very safe as I am well lit and I can see and hear cars from a distance.