When I lived in Los Angeles, the usual mode was that Friday nights were for hitting the bar with work friends to shake off the work week. Saturday nights were for parties and/or date nights.
Here in the Midwest, it seems a lot of parties are held on Friday nights (although Saturday nights are still date nights). The thing about that is: (a) I miss those after work outings, and (2) Friday night parties are often kind of low-key because everyone’s tired after a work week. Saturday night you’ve had a chance to charge your batteries, and you’re ready for what comes before Part B.