I am not quite sure that I have understood your requirement, but I think you are talking about the Rows property of RadCalendar and not RadDateTimePicker. If this is the case, your scenario is not supported out of the box as this Rows can't change dynamically to fill the available space, however you can create your custom code that measure the available space and set the Rows accordingly.
Please excuse me if I have not understood your scenario right. In this case, we will be glad to help if you provide some more info.
the Telerik team
Sharpen your .NET Ninja skills
! Attend Q1 webinar week and get a chance to win a license! Book your seat now >>