GPS下來的時間是“1481267203000”
搜了一下，得到的結果是

int i = 1481267203000;
i = 1481267203000 / 1000;
DateTime t = new DateTime(1970, 1, 1).AddSeconds(i);

後來寫的方法

using System;

public class ConvertDataTimeHelper
{
    /// <summary>
    /// 將DateTime型別轉換為long型別
    /// </summary>
    /// <param name="dt">時間</param>
    ///
 
 <returns></returns>
    public static long ConvertDataTimeLong(DateTime dt)
    {
        DateTime dtStart = TimeZone.CurrentTimeZone.ToLocalTime(new DateTime(1970, 1, 1));
        TimeSpan toNow = DateTime.Now.Subtract(dtStart);
        long timeStamp = toNow.Ticks;
        timeStamp = long
 
.Parse(timeStamp.ToString().Substring(0, timeStamp.ToString().Length - 7));
        return timeStamp;
    }

    /// <summary>
    /// 將Long型別轉換為DateTime型別
    /// </summary>
    /// <param name="d">long</param>
    /// <returns></returns>
    public static DateTime ConvertLongDateTime
 
(long d)
    {
        DateTime dtStart = TimeZone.CurrentTimeZone.ToLocalTime(new DateTime(1970, 1, 1));
        long lTime = long.Parse(d + "0000000");
        TimeSpan toNow = new TimeSpan(lTime);
        DateTime dtResult = dtStart.Add(toNow);
        return dtResult;
    }
}

是不是北京時間就不知道了