第一種方法：就是調(diào)用系統(tǒng)API函數(shù)更改系統(tǒng)時間

 [StructLayout(LayoutKind.Sequential)]
    public struct SystemTime
    {
        public ushort wYear;
        public ushort wMonth;
        public ushort wDayOfWeek;
        public ushort wDay;
        public ushort wHour;
        public ushort wMinute;
        public ushort wSecond;
        public ushort wMiliseconds;
    }
   public class SetSystemDateTime
    {
       [DllImport("Kernel32.dll")]
       public static extern bool SetLocalTime(ref SystemTime sysTime);

       public static bool SetLocalTimeByStr(string timestr)
       {
           bool flag = false;
           SystemTime sysTime = new SystemTime();
           DateTime dt = Convert.ToDateTime(timestr);
           sysTime.wYear = Convert.ToUInt16(dt.Year);
           sysTime.wMonth = Convert.ToUInt16(dt.Month);
           sysTime.wDay = Convert.ToUInt16(dt.Day);
           sysTime.wHour = Convert.ToUInt16(dt.Hour);
           sysTime.wMinute = Convert.ToUInt16(dt.Minute);
           sysTime.wSecond = Convert.ToUInt16(dt.Second);
           try
           {
               flag = SetSystemDateTime.SetLocalTime(ref sysTime);
           }
           catch (Exception e)
           {
               Console.WriteLine("SetSystemDateTime函數(shù)執(zhí)行異常" + e.Message);
           }
           return flag;
       }
    }

第二種方法：就是利用Process類調(diào)用DOC命令更改系統(tǒng)時間

             //實例一個Process類，啟動一個獨立進程
             Process p = new Process(); 
               //Process類有一個StartInfo屬性
             //設(shè)定程序名
             p.StartInfo.FileName = "cmd.exe";
             //設(shè)定程式執(zhí)行參數(shù)    “/C”表示執(zhí)行完命令后馬上退出
             p.StartInfo.Arguments = "/c date 2020-2-20"; 
              //關(guān)閉Shell的使用  
            p.StartInfo.UseShellExecute = false;   
            //重定向標準輸入     
            p.StartInfo.RedirectStandardInput = true; 
            p.StartInfo.RedirectStandardOutput = true;
              //重定向錯誤輸出  
           p.StartInfo.RedirectStandardError = true;  
              //設(shè)置不顯示doc窗口 
            p.StartInfo.CreateNoWindow = true;          
            //啟動
            p.Start(); 

          //從輸出流取得命令執(zhí)行結(jié)果
           return p.StandardOutput.ReadToEnd();

          更多的關(guān)于Process類的操作，可以參考

    http://msdn.microsoft.com/zh-cn/library/system.diagnostics.process_members(VS.80).aspx