accessing records between two dates

I want to access records between two dates... i m using following code...
 da = new OleDbDataAdapter("select * from date1 where start between ' " + dtpstart.Value.ToString() + " '  and ' " + dtpend.Value.ToString() + " '  ", con);
            dt = new DataTable();
            da.Fill(dt);
            dataGridView1.DataSource = dt;


for single month(10/1/2015 - 20/1/2015) i m getting proper records but when when month changes (25/1/2015- 05/2/2015 ), i m nt getting proper records.. i m using ms access for database......plz provide me proper code.. thnk u........