We have a calendar report in our application.  Until recently, it showed the full 24 hours of the day.  At some point in the past few days, however, it started restricting the hours shown to 6AM - 6PM.  As a result, some of our records are being cut off and we are unable to access them through this report.  This is happening across applications, so it is not related to just one report or change we have made.

There doesn't seem to be a way to set what the working hours should be restricted to in any setting.  What am I missing?