Two date structures "sharing" the same date
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Thread: Two date structures "sharing" the same date

  1. #1
    Join Date
    Mar 2014
    Posts
    2

    Two date structures "sharing" the same date

    Hi

    I'm a new C++ programmer (although I've done BV et al for years) so I may be missing something obvious here, but what is wrong with this?

    I have two date/time structures which I'm populating, but when I populate the second one it sets the same values in the first.

    This is what I've got so far


    tm *FirstDate = gmtime(&now);
    tm *SecondDate = gmtime(&now);

    cout <<"Enter your first date in the format dd/mm/yyyy" << endl <<">";
    getline (cin,tempstring);

    FirstDate->tm_mday = atoi(tempstring.substr(0,2).c_str());
    FirstDate->tm_mon = atoi(tempstring.substr(3,2).c_str());
    FirstDate->tm_year = atoi(tempstring.substr(6,4).c_str());

    // this is correct...
    cout<<" your first entered " <<FirstDate->tm_mday << "/" <<FirstDate->tm_mon <<"/" <<FirstDate->tm_year <<endl;
    cout <<"Now enter your second date in the format dd/mm/yyyy" << endl <<">";
    getline (cin,tempstring2);


    SecondDate->tm_mday = atoi(tempstring2.substr(0,2).c_str());
    SecondDate->tm_mon = atoi(tempstring2.substr(3,2).c_str());
    SecondDate->tm_year = atoi(tempstring2.substr(6,4).c_str());

    // at this point they're both the same as the last entry..
    cout<<" your first entered " <<FirstDate->tm_mday << "/" <<FirstDate->tm_mon <<"/" <<FirstDate->tm_year <<endl;
    cout<<" your second entered " <<SecondDate->tm_mday << "/" <<SecondDate->tm_mon <<"/" <<SecondDate->tm_year <<endl;


    What have I missed or misunderstood?

    Cheers

    Sam

  2. #2
    Join Date
    Dec 2012
    Location
    England
    Posts
    2,460

    Re: Two date structures "sharing" the same date

    When posting code, please format your code and use code tags. Go Advanced, select the code and click '#'.

    What have I missed or misunderstood?
    From MSDN http://msdn.microsoft.com/en-us/libr...=vs.60%29.aspx

    The gmtime, mktime, and localtime functions use the same single, statically allocated structure to hold their results. Each call to one of these functions destroys the result of any previous call. If timer represents a date before midnight, January 1, 1970, gmtime returns NULL. There is no error return.
    All advice is offered in good faith only. You are ultimately responsible for effects of your programs and the integrity of the machines they run on.

  3. #3
    Join Date
    Mar 2014
    Posts
    2

    Re: Two date structures "sharing" the same date

    Ahh, thanks 2kaud,

    Still got the VB mindset where you can do this sort of thing. I'll try another approach.

    Sorry about the code insert. I'll know next time

    Sam

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