The current system makes it difficult for schedulers with shift workers. An employee may have booked 'Monday' off, but the employee is still working Sunday nightshift, which overlaps with several hours on Monday morning. Booking 'Monday' off for the employee means taking the Monday nightshift off.

If the employee has booked the day off, and the scheduler adds a shift which overlaps with part of the day - they (the scheduler) should have the ability to proceed with the shift allocation, which if pushed through, should automatically edit the existing time-off booking. Alternatively, if when the scheduler tries to add a shift that overlaps with an existing time-off booking, it could open a dialog window with the time-off booking, and allow the scheduler to edit the time-off on-the-fly.