Like most things at a startup, there are cycles. Sometimes work is 9-6, sometimes its 9-9. Consistency is uncommon, especially at the earlier stages. While you might not have time to date at the moment, you probably will later.
A few points: 1. 9pm is the perfect time to grab a quick bite with friends and head out. There are a ton of great bars / spots which offer a casual environment to be with female / startup / life friends, eat drink and meet guys if you so choose. Ping me for recommendations. 2. The internet (and especially OK Cupid) are great for arranging lots of dates with little effort. 9/10 of the people you meet will be boring or not click, but 1/10 will surprise you. Everyone uses it now, especially as a filler for in between relationships. 3. SF has a great friends-of-friends atmosphere. Go to parties. 4. Learn to love a busy schedule. You can easily cram more into life by going out after work, still getting a good nights sleep, and going back to work the next day. If you're only working M-F, it'll be the most active time of your life.