Hehehe, after some thinking I came up with an even more twisted solution:
Code:
int diff = ((abs(day2 - day1)/(day2 - day1) + 1) / 2 * 365 + day2) - day1
In more bite-sized pieces (or 4-bite pieces, depending on platform):
Code:
int diff = day2 - day1;
int sign = abs(diff) / diff;
int shouldWeAdd365OrNot = (sign + 1) / 2; //1 for yes, 0 for no
int correctedDay2 = day2 + (shouldWeAdd365OrNot * 365);
int finalDiff = correctedDay2 - day1;
Of course, abs() probably uses if internally, but since it's apparently allowed for the assignment.. heck, why not? And, as far as I can see, it strictly uses features that have already been demonstrated to be allowed (i.e. no mod involved, in case that's banned).