C ++，将OADa​​te转换为struct tm

Question

Excel dates are stored as double in a convention that seems to be called OADate , is there a built-in function to convert the OADate to a struct tm .

For example, in Excel, the 9/May/2014 is 41768 . I need in C++ to find a way to convert 41768 in a struct tm initialised to the correct date.

Are there built-in functions to do this ? I could use VariantTimeToSystemTime() but it converts it to a LPSYSTEMTIME which needs then to be converted into a struct tm . I was looking for something that would do both at the same time. It is not very hard to do but I would rather use built-in functions than writing my own.

Answer 1

In the case someone needs to do it, this is enough to make it work:

    double oaDate = 41678.;
    char buffer[256];
    struct tm timeinfo;
    _SYSTEMTIME lpSystemTime;
    VariantTimeToSystemTime(oaDate, &lpSystemTime);
    timeinfo.tm_mday = lpSystemTime.wDay;
    timeinfo.tm_mon = lpSystemTime.wMonth - 1;      // Be careful of different conventions
    timeinfo.tm_year = lpSystemTime.wYear - 1900;
    timeinfo.tm_hour = lpSystemTime.wHour;
    timeinfo.tm_min = lpSystemTime.wMinute;
    timeinfo.tm_sec = lpSystemTime.wSecond;
    timeinfo.tm_isdst = 0;
    mktime(&timeinfo);