Saturday shades it.
After working all week, I can spend a proper and full day with my son, usually at home. More often than not it's Sunday that we'll do things going out and about.
Saturday also brings about sport, and mainly football to watch. Bit of a lie-in, get a few jobs done, maybe go shopping, then sit down and chill for a good few hours with footy on in the background while doing stuff with family.
Friday is the closest, as similar to mentioned above, it's the knowledge that the weekend is just round the corner when work finishes...