I suggest to check this demo
where we use RadWindow's AutoSize feature to adjust the size of the window when the calendar popup is displayed. If you examine the content page's code, you will notice the AdjustRadWindow() function that is called whenever the calendar's popup is shown or closed
i.e.(<ClientEvents OnPopupOpening="AdjustRadWidow" OnPopupClosing="AdjustRadWidow" />)
As for repositioning the popup, I suggest to use the code provided in this help article
as a base and extend it further to fit your requirements.
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