C_求两个日期相隔的天数（闰年）

#include <stdio.h>
#include <math.h>

int leap_year(int year){
    if(year%400==0 || (year%4==0 && year%100!=0)){
        return 1;//是闰年
    }else{
        return 0;//不是闰年
    }
}

int mon_d(int year,int mon){
    int i, days = 0,mon_days[12] = {31,28,31,30,31,30,31,31,30,31,30,31};
    //for(i=1;i<mon;i++){
        if(mon >= 2){
            if(leap_year(year) == 1){
                mon_days[1] = 29;
                for(i=0; i<mon-1; i++){
                     days += mon_days[i];        
                }
                return    days;
            }else{
                for(i=0;i < mon-1;i++){
                     days += mon_days[i];

                }
                return days;
            }
        }        
    //}
    return 0;
}

int main(){

    int y1, m1, d1, y2, m2, d2, i, y, day_to_day = 0;
    printf("请您输入一个日期（eg：2008-8-8）: ");

    scanf("%d-%d-%d",&y1,&m1,&d1);

    printf("请您再输入一个日期（eg：2008-8-8）: ");
    scanf("%d-%d-%d",&y2,&m2,&d2);
    //printf("%d-%d-%d\n",y1,m1,d1);
    //printf("%d-%d-%d\n",y2,m2,d2);

    y = y2-y1;

    if(y == 0){
        day_to_day = mon_d(y2,m2) + d2 - (mon_d(y1,m1) + d1);
    }else if(y == 1){
        day_to_day = 365 + leap_year(y1) - ( mon_d(y1,m1) + d1 ) + mon_d(y2,m2) +d2;
    }else{
        for(i=y1+1; i<y2; i++){
            day_to_day += 365 + leap_year(i);
        }
        day_to_day += 365 + leap_year(y1) - ( mon_d(y1,m1) + d1 ) + mon_d(y2,m2) +d2;;
    }
    printf("这两个日期相差的天数是： %d 天\n",day_to_day);

}