SYSTEMTIME、 time_t、tm 的相互转换

//SYSTEMTIME转time_t
time_t SystemTime2Timet(const SYSTEMTIME& st)
{
struct tm gm = {st.wSecond, st.wMinute, st.wHour, st.wDay, st.wMonth-1, st.wYear-1900, st.wDayOfWeek, 0, 0};
return mktime(&gm);
}

//time_t转SYSTEMTIME
SYSTEMTIME Timet2SystemTime(const time_t& t)
{
tm temptm = *localtime(&t);
SYSTEMTIME st = { 1900 + temptm.tm_year
, 1 + temptm.tm_mon
, temptm.tm_wday
, temptm.tm_mday
, temptm.tm_hour
, temptm.tm_min
, temptm.tm_sec
, 0};
return st;
}