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原贴地址：

http://topic.csdn.net/t/20040707/08/3151675.html

我稍微加工了一下：

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time_t FileTimeToTime_t(const FILETIME &ft)<br /> {<br /> ULARGE_INTEGER ui;<br /> ui.LowPart = ft.dwLowDateTime;<br /> ui.HighPart = ft.dwHighDateTime;<br /> return ((LONGLONG)(ui.QuadPart – 116444736000000000) / 10000000);<br /> }</p> <p>int GetDiffSeconds(const SYSTEMTIME &t1, const SYSTEMTIME &t2)<br /> {<br /> FILETIME fTime1 = { 0, 0 };<br /> FILETIME fTime2 = { 0, 0 };<br /> SystemTimeToFileTime(&t1, &fTime1);<br /> SystemTimeToFileTime(&t2, &fTime2);</p> <p> time_t tt1 = FileTimeToTime_t(fTime1);<br /> time_t tt2 = FileTimeToTime_t(fTime2);</p> <p> return (int)(tt2 – tt1);<br /> }</p> <p>int GetDiffDays(const SYSTEMTIME &t1, const SYSTEMTIME &t2)<br /> {<br /> int diffSeconds = GetDiffSeconds(t1, t2);<br /> return diffSeconds / (24 * 3600);<br /> }</p> <p>

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// 我顺便补充一个：反推SYSTEMTIME隔N天之后的SYSTEMTIME

void Time_tToFileTime(FILETIME &ft, time_t time)<br /> {<br /> ULARGE_INTEGER ui;<br /> ui.QuadPart = (LONGLONG)(time * 10000000) + (LONGLONG)(116444736000000000);<br /> ft.dwLowDateTime = ui.LowPart;<br /> ft.dwHighDateTime = ui.HighPart;<br /> }</p> <p>void GetOffsetDaysTime(const SYSTEMTIME &stSrc, int offDays, SYSTEMTIME &stDst)<br /> {<br /> FILETIME fTimeSrc = { 0, 0 };<br /> SystemTimeToFileTime(&stSrc, &fTimeSrc);<br /> time_t tmSrc = FileTimeToTime_t(fTimeSrc);<br /> time_t tmDst = tmSrc + SEC_OF_DAY * offDays;<br /> FILETIME fTimeDst = { 0, 0 };<br /> Time_tToFileTime(fTimeDst, tmDst);<br /> FileTimeToSystemTime(&fTimeDst, &stDst);<br /> }