Exclude hours from Calendar?
Note: This answer assumes you're using either the day- or the week-display.

On OS X 10.7 and up, the calendar indicates that there are events that aren't displayed on the screen with a tiny "flob" better explained by this screenshot:


You can see that on both the 18th and the 19th there are some events not being shown. These will stay on the screen until you scroll far enough up (or down) to see them.

That said, you can't really "disable" the time interval of 10pm->8am, but you can make space for more events on one screen. To do this, open the Settings (Cmd+,), and select the desired amount of hours to fit into one calendar window. 8am to 10pm is 14 hours, so pick 14.