I tried MSDN DatagridView CalendarColumn sample for entering dates to DataGridView columns.

This control does not allow to set column to null value.
I set ShowCheckBox = true but null value is not stored to grid column.

How allow users to select date OR null value in DataGridView ?

I need to enter whole date form keyboard using as few keystrokes as possibe.
After entering two first digits of data this control requires pressing right arrow for entering next two digits.
How to enable entering whole date without using additional keys ?