c# 处理Excel时间格式问题

很多初学者一开始处理Excel表格的时候，如果遇到处理时间或多或少都会遇到一些坑。
用这种方式处理，就不会出现问题，如下所示：

 /// <summary>
        /// Excel读取为DataTable
        /// </summary>
        /// <param name="strExcelFileName"></param>
        /// <param name="TableName"></param>
        /// <returns></returns>
        public static System.Data.DataTable ExcelToDataTable(string strExcelFileName, string TableName = null)
        {
            //源的定义 
            String strConn = "";
            FileInfo file = new FileInfo(strExcelFileName);
            switch (file.Extension)
            {
                case ".xls":
                    strConn = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + strExcelFileName + ";Extended Properties='Excel 8.0;HDR=Yes;IMEX=1;'";
                    break;
                case ".xlsx":
                    strConn = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" + strExcelFileName + ";Extended Properties='Excel 12.0;HDR=Yes;IMEX=1;'";
                    break;
                default:
                    strConn = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + strExcelFileName + ";Extended Properties='Excel 8.0;HDR=Yes;IMEX=1;'";
                    break;
            }
            //连接数据源 
            OleDbConnection conn = new OleDbConnection(strConn);
            conn.Open();
            DataTable NamesTable = conn.GetOleDbSchemaTable(OleDbSchemaGuid.Tables, null);
            //Sql语句 
            //string strExcel = string.Format("select * from [{0}$]", strSheetName); 这是一种方法 

            string sql = "SELECT * FROM [" + NamesTable.Rows[0][2] + "]";
            if (!string.IsNullOrEmpty(TableName))
            {
                sql = "SELECT * FROM [" + TableName + "$" + "]";
            }
            OleDbDataAdapter adp = new OleDbDataAdapter(sql, strConn);
            DataSet myDataSet = new DataSet();
            adp.Fill(myDataSet);
            DataTable NowDT = myDataSet.Tables[0];
            return NowDT;
        }