显示一个wrong answer,我好奇是哪个数据没法得出正确结果

#include<iostream>
using namespace std;
class DateTime
{
private:
    int year;
    int month;
    int day;
    int hour;
    int minute;
    int second;

public:
    
    int get_time()
    {
        return hour*3600+minute*60+second;
    }
    
    void set_datetime(int y,int m,int d,int h,int min,int sec)
    {
        year=y;
        month=m;
        day=d;
        hour=h;
        minute=min;
        second=sec;
    }
    
    int is_leap_year()
    {
        if(year%400==0 || (year%4==0&&year%100!=0))
            return 1;
        else
            return 0;
    }
    
    int is_leap_year(int i)
    {
        if(i%400==0 || (i%4==0&&i%100!=0))
            return 1;
        else
            return 0;
    }
    
    
    int mid_year(int large_year)//large_year>=year
    {
        int sum=365*(large_year-year-1);//若同年，为-365，减去了till_end和till_start中多出的天数
            for(int i=year+1;i<large_year;i++)
            {
                if(is_leap_year(i))
                    sum++;
            }
            return sum;
    }
        /*
        //int i;
        int sum=0;
        
        int Month[13]={0,31,28+is_leap_year(i),31,30,31,30,31,31,30,31,30,31};
        if(large_year-year<=1)//相等，算天数月份差，差一年，只需要用到till_end和till_start函数
            return 0;
        
        for(int i=year+1;i<large_year;i++)
        {
            for(int j=1;j<=12;j++)
            {
                sum=sum+Month[j];
            }
        }
        return sum;
        */
    //算整的年的天数
    
    int till_end()
    {
        int sum=0;
        int Month[13]={0,31,28+is_leap_year(),31,30,31,30,31,31,30,31,30,31};
        if(month==12)
            return 31-day;
            //return Month[month]-day;
        for(int i=month+1;i<=12;i++)
        {
            sum=sum+Month[i];
        }
        
        return sum+Month[month]-day;
    }
    
    int till_start()
    {
        //int i;
        int sum=0;
        int Month[13]={0,31,28+is_leap_year(),31,30,31,30,31,31,30,31,30,31};
        if(month==1)
            return day;
        
        for(int i=1;i<month;i++)
        {
            sum=sum+Month[i];
        }
        
        return sum+day;
    }
    
    int get_hour()
    {
        return hour;
    }
    
    int get_minute()
    {
        return minute;
    }
    
    int get_second()
    {
        return second;
    }
    
    int get_year()
    {
        return year;
    }
};//实现思路是先算出中间间隔的天数*3600,再加减秒数

int main()
{
    DateTime datetime1,datetime2;
    int y1,m1,d1,h1,min1,sec1;
    int y2,m2,d2,h2,min2,sec2;
    
    cin>>y1>>m1>>d1>>h1>>min1>>sec1;
    cin>>y2>>m2>>d2>>h2>>min2>>sec2;
    
    datetime1.set_datetime(y1,m1,d1,h1,min1,sec1);
    datetime2.set_datetime(y2,m2,d2,h2,min2,sec2);
    
    cout<<(datetime1.till_end()+datetime1.mid_year(datetime2.get_year())+datetime2.till_start())*3600*24+(3600*24-datetime1.get_time())-(3600*24-datetime2.get_time())<<endl;
    //cout<<datetime1.till_end()+datetime1.mid_year(datetime2.get_year())+datetime2.till_start()<<endl;

    system("pause");
    return 0;
}