在C ++中将日期/时间（以Double形式）转换为struct * tm [英] Convert Date/Time (as Double) to struct* tm in C++

问题描述

我从C＃（DateTime.ToOADate（），这是一个OLE日期时间）中获取一个日期/时间作为双精度值。它包含从1899/12/31开始的已过去的日子，其中小数部分是当天的过去部分。乘以86400，我得到了秒数，最后得到了当天的时间。

I get a date/time as double value from C# (DateTime.ToOADate(), which is a OLE Date Time). It contains the passed days from 1899/12/31, with the fraction being the passed part of the day. Multiplied with 86400 I get the seconds and from that finally the day's time.

但是，获取日期比较困难。除了UNIX时间涵盖的日期（1970/01/01至2038/01/19）之外，我仍然没有解决方案。在这段时间内，可以使用mktime（）将过去的日期转换为日期时间。

Getting the date however is harder. I still don't have an solution except for the dates that the UNIX time covers (1970/01/01 to 2038/01/19). During this time, mktime() can be used to convert the passed days to a datetime.

double OleDateTimeValue = 28170.654351851852; // 14.02.1977 15:42:16
struct tm * timeinfo;
int passedDays = (int)OLEDateTimeValue;

// between 1.1.1970 and 18.1.2038
if((passedDays >= 25569) && (passedDays <= 50423)) 
{
    timeinfo->tm_year = 70; //1970
    timeinfo->tm_mon = 0;
    timeinfo->tm_mday = 1 + (passedDays - 25569);
    mktime(timeinfo);
}    
else // date outside the UNIX date/time
{
}

现在，mktime（）格式化tm结构，使其表示请求的日期，如果值在给定日期之外，则返回-1。

Now, mktime() formats the tm struct so that it represents the requested date, or returns -1 if the value is outside the given dates.

有通用的计算方法吗？不幸的是，我不能使用MFC，而必须使用Visual C ++ 6.0。

Is there a generic way to do the calculation? Unfortunately I can't use MFC and have to use Visual C++ 6.0.

谢谢，
Markus

Thanks, Markus

推荐答案

我相信您可以使用 VariantTimeToSystemTime 函数转换为SYSTEMTIME。

I believe you can use the VariantTimeToSystemTime function to convert into a SYSTEMTIME.

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