修改系统时间：

 class APP
    {
        [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;
        }

        [DllImport("kernel32")]
        public static extern Int32 SetSystemTime(ref SystemTime time);
 
        public static void SetDate(DateTime dt)
        {
            SystemTime st;

            st.wYear = (ushort)dt.Year;
            st.wMonth = (ushort)dt.Month;
            st.wDayOfWeek = (ushort)dt.DayOfWeek;
            st.wDay = (ushort)dt.Day;
            st.wHour = (ushort)dt.Hour;
            st.wMinute = (ushort)dt.Minute;
            st.wSecond = (ushort)dt.Second;
            st.wMiliseconds = (ushort)dt.Millisecond;

            SetSystemTime(ref st);
        }
    }