Overlap/Double Booking Management

Smart PHP Calendar has a great event overlap/double booking prevention system. Overlap prevention system can check your calendar groups (personal, shared, group, etc.) or your selected calendars and warns you if there is an overlap.
To manage event overlap

Simple Overlap/Double Booking Management

Simple Overlap/Double Booking Management To use simple overlap/double booking prevention settings

Advanced Overlap/Double Booking Management

Advanced Overlap/Double Booking Management To use advanced overlap/double booking prevention settings