Any time my children aren't peeking over my shoulder! :p Usually mid day, during nap time, in the early morning after my oldest goes to school and before the littles get up, and in the evening after they've gone to bed!
I log on periodically during the day after I get to work. Also in the evening to late night and sometimes during the night if I cannot go back to sleep. I am actually on here most of the time unless we go somewhere or have family issues.
Usually in the evenings...go between here and facebook..Hubby is on one computer and I am on the laptop. Some days I don't get on at all if we have things to do in the evening and I don't get home in time.