C / C++ / MFC

void CMyDlg::GetYesterday() 
{
        // work with the structure SYSTEMTIME to
        // get the local time (which is today)
	SYSTEMTIME st;	
	GetLocalTime(&st);

        // to manipulate time, always convert the SYSTEMTIME to FILETIME
	FILETIME ft;
	SystemTimeToFileTime(&st,&ft);

        // to perform arithmetics actions on time, copy the FILETIME into
        // a ULARGE_INTEGER
	__int64 longTime;
	memcpy(&longTime,&ft,sizeof(longTime));

	// calculate your days as follows:
	// 10000000*60*60*24 = 1 day
	
        // decrease local time with 1 day
	longTime -= (__int64)10000000*60*60*24;
	
        // copy the result back to FILETIME
	memcpy(&ft,&longTime,sizeof(ft));

        // convert FILETIME back to SYSTEMTIME
	FileTimeToSystemTime(&ft,&st);

       // now SYSTEMTIME st holds yesterday 
}

x * 2 == x << 1<br />
x * 4 == x << 2<br />
x * 8 == x << 3

x / 2 == x >> 1<br />
x / 8 == x >> 3

sum+=j*i+1;