C# Covert Excel Serial Date Number to DD/MM/YYYY

When I trying to import the excel to oracle, I encounter a problem when getting the date in a column.
It returns a number "44509.0". It is a serial date number and is the number of days since 1-1-1900.

DateTime.FromOADate(double.Parse(objDS.Tables[0].Rows[i][y].ToString())).ToShortDateString()