select your columns from SQL by naming as date1, date2 and Date3 and in front end for gridview change their caption have the name as date only.
add something like this in your gridview columns section for adding single column multiple times.
<asp :BoundField HeaderText="Date 1" DataField="Date" />
<asp :BoundField HeaderText="Date 2" DataField="Date" />
<asp :BoundField HeaderText="Date 3" DataField="Date" />