Most of us don't schedule too much after 10pm. Then again, some of us hardly set up anything before 10 am. However you run your life, Google Calendar has added a neat Labs feature to make the Day, Week and custom X-Day views less cluttered.
Click the gear icon in the upper-right corner of Calendar, choose Labs, and enable "Hide Morning and Night". Then, head back to your calendar and look for the little bars in the early morning and late evening hours. Drag those up and down, and you can set Google Calendar to compress them down, while still keeping the rare appointment inside them visible.
Hide morning and night hours in Google Calendar [Official Gmail Blog]