判断两个日期相差多少天

#include <iostream>
using namespace std;
#define ISYEAR(x) x%100!=0 && x%4==0 || x%400==0?1:0
int dayOfMonth[13][2]={
    0,0,
    31,31,
    28,29,
    31,31,
    30,30,
    31,31,
    30,30,
    31,31,
    31,31,
    30,30,
    31,31,
    30,30,
    31,31
};

struct Date{
    int Day;
    int Month;
    int Year;
    void nextDay(){
        Day++;
        if(Day>dayOfMonth[Month][ISYEAR(Year)]){
            Day=1;
            Month++;
            if(Month>12){
                Month=1;
                Year++;
            }
        }
    }
};

int buf[5001][13][32];
int Abs(int x){
    return x>0?x:-x;
}

int main(){
    Date tmp;
    int cnt=0;
    tmp.Day=1;
    tmp.Month=1;
    tmp.Year=0;
    while (tmp.Year!=5001) {
        buf[tmp.Year][tmp.Month][tmp.Day]=cnt;
        tmp.nextDay();
        cnt++;
    }
    int d1,m1,y1;
    int d2,m2,y2;
    while (scanf("%4d%2d%2d",&y1,&m1,&d1)!=EOF) {
        scanf("%4d%2d%2d",&y2,&m2,&d2);
        cout<<Abs(buf[y2][m2][d2]-buf[y1][m1][d1]+1)<<endl;
    }
    return 0;
}