How to open DatePicker on clicking the cells of a DataGrid column

Hi,

I want to add DatePicker to a particular column in my databound DataGrid to conveniently select valid dates.  As suggested on this forum in another thread, I used the following article to add Datepicker to my DataGrid:

http://www.c-sharpcorner.com/uploadfile/dpatra/datepicker-in-datagrid-in-wpf/

However, I would like to open the DatePicker window as soon as I click on any cell of my DateTime column.  I also need to only show the date in YYYY-MM-DD format in all the cells of my DateTime column of DataGrid.  The example at the above link is showing date along with time which I don't need. 

I would really appreciate any help.

Thanks.