Calculating days between two dates in C

this is more about coding style

Code:

while(year1 < year2)
        {
[B]            days_in_year = if_leap(year1);
            if(days_in_year == 1)[/B]
                days_until += 366;
            else days_until += 365;
            ++year1;
        }

I'd prefer

Code:

while(year1 < year2)
        {
[B]            if(isLeap(year1))[/B]
                days_until += 366;
            else days_until += 365;
            ++year1;
        }

I could be wrong, I coded c++ before but not C



add on:
say comparing 2011 Dec 1 and 2012 Jan 1
You cannot just add 365/366 days base on the year2 > year1