Find Difference Between Two Dates C

Question

I am trying to take one date away from another in C and find the difference between them in days. However, this is much more complicated than it first appeared to me as I obviously have to allow for differing days in different years due to leap years and a differing numbers of days depending on which month it is. I did try to use time.h but I do not think that it allows for leap years.

Currently my data is stored as integers in an array, for example, {2010, 5, 1, 2011, 6, 1}.

So could someone please post or point me towards an algorithm that will help me achieve this task? Thank you very much.

Try this Already There::http://stackoverflow.com/questions/10309107/c-program-days-between-two-dates — toxic_boi_8041, Jun 25 '14 at 08:36
Possible duplicate: http://stackoverflow.com/questions/14218894/number-of-days-between-two-dates-c — Ilya, Jun 25 '14 at 08:36
@YuHao I tried to find the difference between two dates in days between the first of Feb and the first of March using time.h, once for a leap year and once for a non leap year, and they returned the same answer, which is incorrect — Jamie1596, Jun 25 '14 at 08:43
You might have been on a non-conforming implementation, or perhaps you made a mistake in your use of `mktime`. Post the program that appears to show the wrong result! — M.M, Jun 25 '14 at 08:49
@Jamie1596: Sorry, but I suspect an error on your part. If you are absolutely sure your code is correct then you should file a bug report with your OS vendor. But I doubt this vital part is broken: a _lot_ of people would usually notice. For example, have you set the correct timezone for your calculations? — DarkDust, Jun 25 '14 at 08:50
@DarkDust: Yeah, it is looking that way. Thanks for your help. — Jamie1596, Jun 25 '14 at 08:52
look here http://stackoverflow.com/questions/19035748/difference-between-two-date-in-c?rq=1 — Jayesh Bhoi, Jun 25 '14 at 09:16
Upvoted because this a Very Good Question. There are answers already on SO for many other languages, e.g. a [simple answer for C#](http://stackoverflow.com/questions/1607336/calculate-difference-between-two-dates-number-of-days). That question is upvoted heavily no doubt due to the simplicity of the answer, and I suspect that this question for C is downvoted multiple times because the answer is not simple, i.e. because the downvoters think it reflects badly on C. Don't do that, please. — Cheers and hth. - Alf, Jul 10 '15 at 00:25

score 5 · Accepted Answer · edited May 23 '17 at 10:29

5

The standard library C Time Library contains structures and functions you want.

This header file contains definitions of functions to get and manipulate date and time information.

Also check C date and time functions and C program days between two dates

EDIT:-

Try this:

int main()
{
    int day1,mon1,year1,day2,mon2,year2;
    int ref,dd1,dd2,i;
    clrscr();
    printf("Enter first date  day, month, year\n");
    scanf("%d%d%d",&day1,&mon1,&year1);
    printf("Enter second date day, month, year\n");
    scanf("%d%d%d",&day2,&mon2,&year2);
    ref = year1;
    if(year2<year1)
    ref = year2;
    dd1=0;
    dd1=dater(mon1);
    for(i=ref;i<year1;i++)
    {
        if(i%4==0)
        dd1+=1;
    }
    dd1=dd1+day1+(year1-ref)*365;
    dd2=0;
    for(i=ref;i<year2;i++)
    {
        if(i%4==0)
        dd2+=1;
    }
    dd2=dater(mon2)+dd2+day2+((year2-ref)*365);
    printf("\n\n Difference between the two dates is %d days",abs(dd2-dd1));

    getch();
}

int dater(x)
{ int y=0;
    switch(x)
    {
        case 1: y=0; break;
        case 2: y=31; break;
        case 3: y=59; break;
        case 4: y=90; break;
        case 5: y=120;break;
        case 6: y=151; break;
        case 7: y=181; break;
        case 8: y=212; break;
        case 9: y=243; break;
        case 10:y=273; break;
        case 11:y=304; break;
        case 12:y=334; break;
        default: printf("Invalid Input\n\n\n\n"); exit(1);
    }
    return(y);
}

or using time.h try like this:

#include <stdio.h>  
#include <time.h>       
int main ()
{
  struct tm start_date;
  struct tm end_date;
  time_t start_time, end_time;
  double seconds;

  start_date.tm_hour = 0;  start_date.tm_min = 0;  start_date.tm_sec = 0;
  start_date.tm_mon = 10; start_date.tm_mday = 15; start_date.tm_year = 113;

  end_date.tm_hour = 0;  end_date.tm_min = 0;  end_date.tm_sec = 0;
  end_date.tm_mon = 10; end_date.tm_mday = 20; end_date.tm_year = 113;

  start_time = mktime(&start_date);
  end_time = mktime(&end_date);

  seconds = difftime(end_time, start_time);

  printf ("%.f seconds difference\n", seconds);

  return 0;
}

edited May 23 '17 at 10:29

Community

1
1

answered Jun 25 '14 at 08:38

Rahul Tripathi

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Does difftime take into account leap years then? I think when I tried using that library before, I just took away the two dates, which may be the problem. – Jamie1596 Jun 25 '14 at 08:50
@Jamie1596:- Without looking your code it is hard to predict what was your problem! ;) – Rahul Tripathi Jun 25 '14 at 08:52
Just out of interest, how would you find the difference between two dates using the time.h library? I'm having a bit of trouble figuring out how to define the time and then make it or something. – Jamie1596 Jun 25 '14 at 09:05
@Jamie1596:- Did you checked the link which contains the leap year time difference calculation? Does that help? – Rahul Tripathi Jun 25 '14 at 09:06
@Jamie1596:- I have updated my answer. Hope that helps! – Rahul Tripathi Jun 25 '14 at 09:09
I thought you said that the library could do it using one of its functions. The answers on that page are longer than just using that library to work it out. Or have I misunderstood something? – Jamie1596 Jun 25 '14 at 09:09
Thanks for your updated answer, but I'm confused; can I not use the time.h library? – Jamie1596 Jun 25 '14 at 09:11
@Jamie1596:- Updated the answer with time.h library as well! Does that help? – Rahul Tripathi Jun 25 '14 at 09:13
Thank you very much...again. Which method would you recommend though? – Jamie1596 Jun 25 '14 at 09:14
@Jamie1596:- Both are good. I would go with the second choice. But again thats my choice. And if this helps then do accept this as an answer! – Rahul Tripathi Jun 25 '14 at 09:16
Why the first choice? The second looks much simpler? – Jamie1596 Jun 25 '14 at 09:20
@Jamie1596:- Sorry that was a typo! – Rahul Tripathi Jun 25 '14 at 09:21

score 3 · Answer 2 · answered Jun 25 '14 at 08:52

3

Algo:

Convert dates to struct tm.
Convert struct tm to time_t.
Take the difference between the time_ts. It yields the difference between dates in seconds.
Divide the difference in seconds by 86400 to convert it to days.

answered Jun 25 '14 at 08:52

Maxim Egorushkin

131,725
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score -1 · Answer 3 · edited Dec 30 '14 at 09:49

/* This function calculates the differance between two dates, passes 6 parameters date-month-year of first date and date-month-year of second date and prints the difference in date-weeks-year  format */
void Date::subtract(int firstDate, int firstMonth, int firstYear,int secondDate, int secondMonth, int secondYear)
{
/*check the dates are valid or not  */
if(isDateValid(firstDate,firstMonth,firstYear) && isDateValid(secondDate,secondMonth,secondYear) )
{

    firstMonth = (firstMonth + 9) % 12;
    firstYear = firstYear - firstMonth / 10;
    FirstNoOfDays = 365 * firstYear + firstYear/4 - firstYear/100 + firstYear/400 + (firstMonth * 306 + 5) /10 + ( firstDate - 1 );

    secondMonth = (secondMonth + 9) % 12;
    secondYear = secondYear - secondMonth / 10;
    SecondNoOfDays = 365 * secondYear + secondYear/4 - secondYear/100 + secondYear/400 + (secondMonth * 306 + 5) /10 + ( secondDate - 1 );

    dayDifference = abs(FirstNoOfDays - SecondNoOfDays); /* uses absolute if the first date is smaller so it wont give negative number */
    years = dayDifference / 365;
    weeks = (dayDifference % 365)/7;
    days = (dayDifference % 365) % 7;
    cout<<years<<" years "<<weeks<<" weeks "<<days<< " days"<<endl;

}
else
{
    cout<<"Invalid Date"<<endl;
}

}

Find Difference Between Two Dates C

3 Answers3