Workplace Calendar

I am asking for ideas as to how to proceed with using an events calendar for a system in which:

1. an employer can add holidays and non-working days as events
2. when an employee applies for vacation, the employee provides a start date and the number of days of vacation desired.
3. The system calculates the end date of vacation - ignoring the holidays and non-working days for the chosen period.

Any assistance would be greatly appreciated.