From about 12:30pm to about 1:00am. Sometimes, like now, in the middle of the night due to insomnia. I get the housework, errands and serious design work at my shop done in the mornings. Afternoons are pretty difficult for me energywise. I am hypoglycemic and my blood sugar does not usually rise until about 6pm.
I'm mostly on between 6:30 AM and 6 PM, Monday through Friday. It really depends on what's going on, but of course it's also inline with our office hours so I can get to other team members when you all need things taken care of around here.