I think it depends on the person and your schedule. Unless you're able to do it all at the same time, it seems best to break down your housework into different tasks and tackle them on different days. Doing that prevents you from having to block off a large chunk of time to accomplish everything, but also gives you a routine to make sure it's getting done. I have a hub about home management that gives some practicals for making a cleaning schedule that could also be helpful. Ultimately, though, I would say the "best time" depends on your personality (when you're most productive) and your schedule (the times it's physically possible).