【转】VC++计算当前时间点间隔N天的时间(不使用CTimeSpan类)

　　转自：http://blog.csdn.net/fzuim/article/details/61199351

　　涉及到有效期的设置，需要计算N天时间间隔的时间。

 C++ Code 

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#define QUADPART        10000000i64

SYSTEMTIME CalTime(int nTimeSpan)
{
SYSTEMTIME sysCurTime;
SYSTEMTIME sysOutTime;
GetLocalTime(&sysCurTime);
LONGLONG lTimeSpan = nTimeSpan * QUADPART * 86400;
LARGE_INTEGER fTime;
SystemTimeToFileTime(&sysCurTime, (FILETIME*)&fTime);
fTime.QuadPart += lTimeSpan;
FileTimeToSystemTime((FILETIME*)&fTime, &sysOutTime);

  return sysOutTime;
}

　　上面代码就只计算天数间隔，若要类似CTimeSpan( LONG lDays, int nHours, int nMins, int nSecs )计算到时分秒，则传参需要采用类似CTimeSpan类的方式构造个CArTimeSpan( LONG lDays, int nHours, int nMins, int nSecs );用成员变量存储对应的天时分秒

 C++ Code 

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LONGLONG lTimeSpan  = v_ArTimeSpan.m_iDays * QUADPART * 86400 +
                     v_ArTimeSpan.m_iHours * QUADPART * 3600 +
                     v_ArTimeSpan.m_iMins * QUADPART * 60 +
                     v_ArTimeSpan.m_iSecs * QUADPART;