A supervisor should be able to put a shift on a calendar that has an additional availability indication set up for the whole day.

When an employee makes themselves available for additional hours on their calendar and chose the entire day/24 hours, the entire day on the calendar turns green. This green bar is preventing supervisors from building an OT schedule direct on the weekly view calendar. There is a workaround available to the supervisor by changing the calendar to a monthly view and adding a shift. 

Engineering has determined this is an issue that won't be fixed as there is a viable workaround. However, customer is wanting this issue to be fixed.

See JIRA RAPD - 11245 for reference.