C语言写的日期比较

最近无聊,写了一个日期比较的C程序,发上来供大家拍砖!

#include <stdio.h>

bool isRun(int year);
int year(int year1,int year2);
int month(struct day day1,struct day day2);
int day(int day1,int day2);

struct day{
	int year;
	int month;
	int day;
};

int main(){
	
	int def;
	struct day day1={2009,3,9},day2={1986,8,26};
	if(day1.year<day2.year){
		printf("输入有误,请将大数放在前面!");
	}else if((day1.year==day2.year)&&(day1.month<day2.month)){
		printf("输入有误,请将大数放在前面!");
	}else if((day1.year==day2.year)&&(day1.month==day2.month)&&(day1.day<day2.day)){
		printf("输入有误,请将大数放在前面!");
	}else{
		def=year(day1.year,day2.year)+month(day1,day2)+day(day1.day,day2.day);
		printf("两个时间的差值为:%d",def);
	}
	
}

//bool isRun(int year);
//返回年差数
int year(int year1,int year2){
	int def = year1-year2;
	int i;
	int result=0;//年值
	for(i=0;i<def;i++){
		if(isRun(year1+i)){
			//为闰年
			result=result+366;
		}else{
			//为平年
			result=result+365;
		}
	}
	
	return result;
	
}


int monthToJanaray(int year,int month);
 
//返回月差数
int month(struct day day1,struct day day2){
	int num1=monthToJanaray(day1.year,day1.month);
	int num2=monthToJanaray(day2.year,day2.month);
	return num1-num2;
}


//返回日差数
int day(int day1,int day2){
	return day1-day2;
}


int yearMonthToDay(int year,int month);
//返回一年中某月到一月的天数
int monthToJanaray(int year,int month){
	int i;
	int day=0;
	for(i=month-1;i>0;i--){
		day=day+yearMonthToDay(year,i);
	}
	return day;
}


//bool isRun(int year);
//返回一年中一个月的天数
int yearMonthToDay(int year,int month){
	int i;//一年中的某个月的天数
	int leap;
	int days[2][12]={
		{31,28,31,30,31,30,31,31,30,31,30,31},
		{31,29,31,30,31,30,31,31,30,31,30,31}
	};
	if(isRun(year)){
		//为闰年
		leap=1;
	}else{
		//为平年
		leap=0;
	}
	i=days[leap][month-1];
	return i;
}


//判断是否闰年
bool isRun(int year){
	int i =year;
	if((i%4==0&&i%100== 0)||i%400==0){
		//为闰年
		return true;
	}else{
		//为平年
		return false;
	}
}