The ID property indicates the identifier of the Group. A Group object may hosts multiple Event objects, when the GroupID for each event is the same as the ID property. The ID parameter of the Add method indicates the ID of the Group being added. You can use the Item property of the Groups collection to access a group giving its identifier. Use the GroupID property of the NonworkingTime object to apply the non-working time to the specified groups. 

The control displays groups if:

• ShowGroupingEvents property is True
• The Groups collection has elements. By default, the Groups collection contains no Group objects.

If the control displays groups the GroupID property of the newly created event is automatically updated with the group where the event has been created. The AllowMoveEventToOtherGroup property specifies whether the user can move an event from a group to another at runtime. Use the Add method of the Groups collection to add new groups to the control.