Question

I am trying to create a program that finds out how many months they have been alive, but have been running into some issues. Here is my function so far:

int getResult(int year, month, day, endResult)
{
    int thisYear, thisMonth, thisDay;

    year = thisYear - year;

    year *= 12;
}

And what I’m trying to accomplish would show an output like:

Output: 
What year were you born? 
1989 
What month were you born? 
5 
What day were you born? 
23 
You are x months old.

I was going to continue with months but then I realized, what if the month they were born is in after this month or before? So, if anyone has any tips on how to calculate that, I’d appreciate it.

Answer 1

Let’s see. First, let’s say now is:

year_now and month_now

and your birthday is:

year_birth and month_birth

Now, we go case by case:

• month_now == month_birth: as you have already computed:

  months_old = (year_now-year_birth)*12
  

• month_now > month_birth: easily, you have:

  months_old = (year_now-year_birth)*12 + (month_now-month_birth)
  

• month_now < month_birth: in this case, (year_now-year_birth)*12 gives you more months then necessary, and you have to subtract:

  months_old = (year_now-year_birth)*12 - (month_birth-month_now)
  

Now if you look carefully, you will see that they are all in fact the same formula:

months_old = (year_now-year_birth)*12 + (month_now-month_birth)

(in the third case, month_now-month_birth is negative)