DateTime

 固定輸出格式 yyyy/MM/dd tt hh:mm:ss (如 2023/10/31 下午 05:34:02

Thread.CurrentThread.CurrentCulture = CultureInfo.GetCultureInfo("en-US");

string xxx = ooo.ToString("yyyy/MM/dd tt hh:mm:ss");

if (xxx.IndexOf("AM") >= 0)

{

    xxx = xxx.Replace("AM", "上午");

}

else if (xxx.IndexOf("PM") >= 0)

{

    xxx = xxx.Replace("PM", "下午");

}