它通常工作，但在4，6，9和11个月的任何特定日期，它只是跳到下一个月的第一天。

#include <iostream>
using namespace std;

int main()
{
    cout << "What is the day after the date you enter?:";
        int day, month, year;
    cin >> day >> month >> year;
    if (day == 31 && month == 12)
    {
        day = 1;
        month = 1;
        year = year + 1;
    }
    else if (day == 31 && month == 1 || month == 3 || month == 5 || month == 7 || month == 8 || month == 10)
    {
        day = 1;
        month = month + 1;
    }
    else if (day == 30 && month == 4 || month == 6 || month == 9 || month == 11)
    {
        day = 1;
        month = month + 1;
    }
    else if (day == 28 && month == 2)
    {
        day = 1;
        month = month + 1;
    }
    else if (day == 29 && month == 2)
    {
        day = 1;
        month = month + 1;
    }
    else
    {
        day = day + 1;
    }
    cout << "The day after the date you entered is: " << day << "/" << month << "/" << year << endl;
    return 0;
    system("pause");
}

`
例如，我使用的第一个日期是14 09 2020，它输出1/10/2020
this is a picture for proof
Idk怎么办，请帮助