If you DataType is DateTime & Using with C#.Try the Following Code to set a value.
There is a CustomFormat Property for the DatePicker control that is needed to be specified.
dtpBlockStartDate.CustomFormat = "dd-MMM-yyyy";
ds refers to dataset & i am suposing that it is in first column.
Try To debug it .SomeWhere you might be resetting it to Currrent Date
If any Problem Then Paste Your Complete Code
Hope It Helps You