You will prompt a user for a month, a day and a year. You will then tell the user how many days since January 1 of that year the input date is. For example if the user inputs a 3 for the month, a 2 for the date, and 2000 for the year the program outputs the number of days as being 62. Note 2000 is a leap year. Therefore you must test to see if a year is a leap year when doing this problem.

I'm trying to build onto this one:

#include<iostream>

using namespace std;

int main()
{
int days_in_months[] = { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };

int day;

int month;

int year;

int days_difference;

int reg_year = 365;

int leap_year = 366;



cout << "Program to calculate how many days are in between the date and the start of the year." << endl;
cout << endl;

cout << "Please enter the date by day, month, year." << endl;
cout << endl;

cout << "First date:: " << endl;
cout << endl;

cout << "Day: ";
cin >> day;
if (day > 31 || day <= 0)
{
    cout << "Incorrect day entered" << endl;
    cin.ignore();
    return 0;
}
cout << "Month: ";
cin >> month;
if (month > 12 || month <= 0)
{
    cout << "Incorrect Month entered" << endl;
    cin.ignore();
    return 0;
}
cout << "Year: ";
cin >> year;

if (year > 9999 || year < 0)
{
    cout << "Incorrect year entered" << endl;
    cin.ignore();
    return 0;

or just edit this one:

#include<iostream>

using namespace std;

int main()
{
int days_in_months[] = { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };

int first_day, second_day;

int first_month, second_month;

int first_year, second_year;

int years_difference, days_difference;

int months_total;

int reg_year = 365;


cout << "Program to calculate how many days are in between the day/month/year entered." << endl;
cout << endl;

cout << "Please enter the date by day, month, year." << endl;
cout << endl;

cout << "First date:: " << endl;
cout << endl;

cout << "Day: ";
cin >> first_day;
if (first_day > 31 || first_day <= 0)
{
    cout << "Incorrect day entered" << endl;
    cin.ignore();
    return 0;
}
cout << "Month: ";
cin >> first_month;
if (first_month > 12 || first_month <= 0)
{
    cout << "Incorrect Month entered" << endl;
    cin.ignore();
    return 0;
}
cout << "Year: ";
cin >> first_year;

if (first_year > 9999 || first_year < 0)
{
    cout << "Incorrect Year Entered" << endl;
    cin.ignore();
    return 0;
}

cout << endl;
cout << "\nSecond date:: " << endl;
cout << endl;

cout << "Day: ";
cin >> second_day;
if (second_day > 31 || second_day <= 0)
{
    cout << "Incorrect day entered" << endl;
    cin.ignore();
    return 0;
}
cout << "Month: ";
cin >> second_month;
if (second_month > 12 || second_month <= 0)
{
    cout << "Incorrect Month entered" << endl;
    cin.ignore();
    return 0;
}
cout << "Year: ";
cin >> second_year;
if (second_year > 9999 || second_year < 0)
{
    cout << "Incorrect Year Entered" << endl;
    cin.ignore();
    return 0;
}


/////////////////////////////Years/////////////////////////////////


if (first_year == second_year)
{
    years_difference = 0;
}
else

{
    if (first_year % 4 == 0 && first_year % 100 != 0 || first_year % 400 == 0)
    {
        if (second_year % 4 == 0 && second_year % 100 != 0 || second_year % 400 == 0)
        {
            if (first_year > second_year)
            {
                years_difference = (first_year - second_year) * (reg_year)+2;
            }
            else
            {
                years_difference = (second_year - first_year) * (reg_year)+2;
            }
            if (second_month > first_month)
            {
                if (days_in_months[first_month - 1] > days_in_months[1])
                {
                    --years_difference;
                }
            }
        }
        else
        {
            if (first_year > second_year)
            {
                years_difference = (first_year - second_year) * (reg_year)+1;
            }
            else
            {
                years_difference = (second_year - first_year) * (reg_year)+1;

            }
            if (first_month > second_month)
            {
                if (days_in_months[second_month - 1] > days_in_months[1])
                {
                    --years_difference;
                }
            }
        }
    }
    else

    {
        if (first_year > second_year)
        {
            years_difference = (first_year - second_year) * (reg_year);
        }
        else
        {
            years_difference = (second_year - first_year) * (reg_year);
        }
    }
}

/////////////////////////////Months////////////////////////////////////


if (first_month == second_month)
{
    months_total = 0;
}
else
{
    if (first_month > second_month)
    {
        for (int i = (first_month - 1); i > (second_month - 1); i--)
        {
            static int months_total_temp = 0;
            months_total_temp += days_in_months[i];
            months_total = months_total_temp;
        }
    }
    else
    {
        for (int i = (first_month - 1); i < (second_month - 1); i++)
        {
            static int months_total_temp = 0;
            months_total_temp += days_in_months[i];
            months_total = months_total_temp;
        }
    }
}

////////////////////////////Days//////////////////////////////////

int days_total;

if (first_day == second_day)
{
    days_difference = 0;
    days_total = (years_difference + months_total) - days_difference;
}
else
{
    if (first_day > second_day)
    {
        days_difference = first_day - second_day;
        days_total = (years_difference + months_total) - days_difference;
    }
    else
    {
        days_difference = second_day - first_day;
        days_total = (years_difference + months_total) + days_difference;
    }
}

//////////////////////////In Between Leap Years///////////////////////////////

if (first_year == second_year)
{
}
else
{
    if (first_year > second_year)
    {
        for (int i = (second_year + 1); i < first_year; i++)
        {
            if (i % 4 == 0 && i % 100 != 0 || i % 400 == 0)
            {
                cout << endl;

                cout << i << endl;
                ++days_total;
            }
        }
    }
    else
    {
        for (int i = (first_year + 1); i < second_year; i++)
        {
            if (i % 4 == 0 && i % 100 != 0 || i % 400 == 0)
            {
                cout << endl;
                cout << i << endl;
                ++days_total;
            }
        }
    }
}

//////////////////////////Output//////////////////////////////////


cout << endl;
cout << "\nThe total days in between your dates are: " << days_total << endl;
cout << endl;

cin.get();
cin.ignore();
return 0;
}