C++ calculate difference between dates

Question

Possible Duplicate:
Checking two TDateTime variables

I am having trouble calculating the difference between two dates and then displaying the difference. I have posted a previous question.

I am after help with the replaceTime function. I am not sure how/why I need to use this.

Here is my code:

TDateTime testFirstDate("11/09/2012");
TDateTime testFirstTime("14:00");

TDateTime testSecondDate("12/09/2012");
TDateTime testSecondTime("16:00");

TDateTime testCombined1 = ReplaceTime(testFirstDate,testFirstTime);
TDateTime testCombined2 = ReplaceTime(testSecondDate,testSecondTime);

TDateTime testDateDifference = testCombined2 - testCombined1;

std::cout << testDateDifference;

You do not need to repost the same question more than once: [Checking two TDateTime variables](http://stackoverflow.com/questions/12386266/checking-two-tdatetime-variables) — Adriano Repetti, Sep 12 '12 at 14:53
It looks to me as if ReplaceTime is being used to combine a date and a time. You need to combine testFirstDate and testFirstTime and also testSecondDate and testSecondTime before you find the difference, no? — john, Sep 12 '12 at 16:22
Yes. Basically, I am wanting to know if the second time and date is later than the first time and date. — Darryl Janecek, Sep 13 '12 at 03:06

score 0 · Answer 1 · answered Sep 12 '12 at 14:58

0

Your code doesn't make sense. The difference of two dates is never a new date!

I suspect that this part is wrong:

TDateTime testDateDifference = testCombined2 - testCombined1;

The difference of two dates is a period of time--a time span (usually in seconds). Did you write the implementation for TDateTime yourself?

answered Sep 12 '12 at 14:58

Man Vs Code

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It's the implementation of TDateTime of C++ Builder libraries. His code is right, the difference between two dates is another date. – Adriano Repetti Sep 12 '12 at 15:52
`Use the System::TDateTime::- to subtract the value specified by the rhs operand from the System::TDateTime::TDateTime object. The rhs operand represents the number of days (including fractional days) to subtract.` According to the Borland spec, although the type is a TDateTime the rhs operand is technically not a date. This is how they can get away with operator-() returning a new date. At least .NET got this right with their DateTime class. – Man Vs Code Sep 13 '12 at 20:23

C++ calculate difference between dates

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