#include <iostream>
#include <cassert>
using namespace std;

int julianDateCalc(int x, int y);

int daysPerMonth[12] = {31,28,31,30,31,30,31,31,30,31,30,31};

int main()
{
    int firstDay, secondDay, firstMonth, secondMonth = 0;

    //Read in dates by the user.
    cout << "Please enter two dates in number format (dd mm)" << endl;
    cout << "Day: ";
    cin >> firstDay;
    cout << "Month: ";
    cin >> firstMonth;
    cout << endl;
    cout << "Day: ";
    cin >> secondDay;
    cout << "Month: ";
    cin >> secondMonth;
    cout << endl;

    //Check validity of date entered.
    assert(firstDay > 0 && firstDay < (daysPerMonth[firstMonth - 1] + 1));
    assert(secondDay > 0 && secondDay < (daysPerMonth[secondMonth - 1] + 1));

    //Function calls for the Julian conversion.
    julianDateCalc(firstDay, firstMonth);
    julianDateCalc(secondDay, secondMonth);

    //Check to determine which date is lower/higher and calculate difference in days between the dates.
    if (julianDateCalc(firstDay, firstMonth) > julianDateCalc(secondDay, secondMonth))
    {
        cout << "The first date converted is: " << julianDateCalc(firstDay, firstMonth) << endl;
        cout << "The second date converted is: " << julianDateCalc(secondDay, secondMonth) << endl;
        cout << endl;
        cout << " The difference in days between the two dates is: " << julianDateCalc(firstDay, firstMonth) - julianDateCalc(secondDay, secondMonth) << " days" << endl;
    }
    else
    {
        cout << "The first date converted is: " << julianDateCalc(firstDay, firstMonth) << endl;
        cout << "The second date converted is: " << julianDateCalc(secondDay, secondMonth) << endl;
        cout << endl;
        cout << "The difference in days between the two dates is: " << julianDateCalc(secondDay, secondMonth) - julianDateCalc(firstDay, firstMonth) << " days" << endl;
    }

    return 0;
}

//Function to calculate the Julian date of the user's entry.
int julianDateCalc(int day, int month)
{
    int sum = 0;

    for (int i = 0; i < month - 1 ; i++)
    {
        sum += daysPerMonth[i];
    }

    return sum + day;
}