我想让WINCC和PLC的时间同步！

#pragma code("kernel32.dll");
void SetSystemTime(SYSTEMTIME *lpst);
#pragma code();

SYSTEMTIME time;

time.wYear=GetTagWord("DB7_year");
time.wMonth=GetTagWord("DB7_month");
time.wDay=GetTagWord("DB7_day");
time.wHour=GetTagWord("DB7_hour");
time.wMinute=GetTagWord("DB7_minute");
time.wSecond=GetTagWord("DB7_second");

if(SetSystemTime(&time))
MessageBox(NULL,"sucess","ok",MB_OKMB_ICONEXCLAMATIONMB_SETFOREGROUNDMB_SYSTEMMODAL);
else
MessageBox(NULL,"fail","error",MB_OKMB_ICONEXCLAMATIONMB_SETFOREGROUNDMB_SYSTEMMO

程序执行是正确的！返回的消息是对的。但时间没有变化
我在IO field显示读PLC的时间DB7也是正确的！为什么？