Hi Jay,
Matthew is correct that currently there isn't a native option to limit the hours of your Calendar but our team is looking for additional features with our Calendars that would be helpful to our Customers. If you feel this would be a beneficial feature in Quick Base, I would encourage you to submit feedback regarding this via our Feedback Platform - UserVoice - Which can most easily be accessed from the My Apps page in Quick Base by clicking on the orange Feedback tab or at
http://quickbase.uservoice.com . This forum is used by our development team to explore customer suggestions for enhancements / changes to the platform. Many of the items that have been suggested by customers have already been incorporated into Quick Base and I would encourage you to participate as well.