C# 日期轉換

//日期轉換簡易
   string strBeginDay = DateTime.Now.ToString("yyyy/MM/dd");
   string strEndDay = DateTime.Now.AddMonths(-3).ToString("yyyy/MM/dd");

   //日期轉換進階
   string strD1 = aryFields[3,1].ToString() + aryFields[4,1].ToString();
   DateTime dt = DateTime.ParseExact(strD1,"yyyyMMddHHmmss",System.Globalization.CultureInfo.CurrentCulture);
   strD1  = dt.ToString("yyyy/MM/dd HH:mm:ss");