Leap year calculation

leapYear.c

/*
 * 1 - is
 * 0 - is not
 */
int a2gs_AddSubDate_isLeapYear(int year)
{
	if(year % 4 == 0){
		if(year % 100 == 0){
			if(year % 400 == 0)
				return(1);
			return(0);
		}
		return(1);
	}

	return(0);
}

#include <stdio.h>

int a2gs_AddSubDate_isLeapYear(int year);

int main(int argc, char *argv[])
{
	printf("1900 [%s]/no\n" , a2gs_AddSubDate_isLeapYear(1900) ? "yes" : "no");
	printf("1997 [%s]/no\n" , a2gs_AddSubDate_isLeapYear(1997) ? "yes" : "no");
	printf("2000 [%s]/yes\n", a2gs_AddSubDate_isLeapYear(2000) ? "yes" : "no");
	printf("2010 [%s]/no\n" , a2gs_AddSubDate_isLeapYear(2010) ? "yes" : "no");
	printf("2011 [%s]/no\n" , a2gs_AddSubDate_isLeapYear(2011) ? "yes" : "no");
	printf("2012 [%s]/yes\n", a2gs_AddSubDate_isLeapYear(2012) ? "yes" : "no");
	printf("2013 [%s]/no\n" , a2gs_AddSubDate_isLeapYear(2013) ? "yes" : "no");

	return(0);
}

cc -o test test.c -g -std=c11 -Wall -Wextra -D_XOPEN_SOURCE=700 -D_POSIX_C_SOURCE=200809L -D_POSIX_SOURCE=1 -D_DEFAULT_SOURCE=1 -D_GNU_SOURCE=1

A better solution:

int a2gs_AddSubDate_isLeapYear(int year)
{
	int m4, m100, m400;

	m4 = year % 4;
	m100 = year % 100;
	m400 = year % 400;

	if(((m4 == 0) && (m100 == 0) && (m400 == 0)) || ((m4 == 0) && (m100 != 0)))
		return(1);

	return(0);
}