These are events that are marked as "all-day" events.

In order to enable it you need to do the following:

• Specify the data source field in DataAllDayField (all-day events will have true value in that field).
• Turn on the all-day header by setting ShowAllDayEvents to true.

You can use the following properties to tune the appearance:

• AllDayEventHeight will specify the all-day event box height. The total all-day header height will be stretched to show all the all-day events.
• AllDayEventBackColor specifies the background color of the event boxes.

At this moment, all-day events have some limitations:

• It's not possible to move and resize them (including drag&drop from the time table or from outside of the calendar).
• It's not possible to select them (when EventClickHandling="Select").
• It's not possible to edit the text inline.

Passive event-related events are allowed:

• EventClick
• EventRightClick
• EventContextMenuClick (context menu is supported)

Basically, it's a read-only area at the moment. I would like to extend the support in the future but I can't give a specific date at the moment (2-3 months).