You can enable event overlap protection using allowEventOverlap config property. This will forbid placing an event at a location with existing events. This rules is enforced during the following drag and drop operations:
See Also
JavaScript
Example
<div id="dp"></div> <script> var dp = new DayPilot.Calendar("dp"); dp.allowEventOverlap = false; // ... dp.init() </script>
ASP.NET WebForms
Example
<DayPilot:DayPilotCalendar id="DayPilotCalendar1" runat="server" AllowEventOverlap="false" ... />