#include <iostream>
#include <cstdlib>
#include <ctime>    //for the functions time and localtime
using namespace std;

const int date_length[] {
	 0,   //dummy, so that January will have subscript 1
	31,   //January
	28,   //February.  Pretend there are no leap years.
	31,   //March
	30,   //April
	31,   //May
	30,   //June
	31,   //July
	31,   //August
	30,   //September
	31,   //October
	30,   //November
	31    //December
};

//Function declarations.
void date_print(const int *pyear, const int *pmonth, const int *pday);
void date_next(int *pyear, int *pmonth, int *pday, int n);
void date_next(int *pyear, int *pmonth, int *pday);

int main()
{
	const int independenceDayYear {1776};  //July 4, 1776
	const int independenceDayMonth {7};
	const int independenceDayDay {4};
	date_print(&independenceDayYear, &independenceDayMonth, &independenceDayDay);
	cout << " is Independence Day.\n";

	//Ask the operating system for the current date and time.
        const time_t t {time(nullptr)};
        const tm *const p {localtime(&t)};

	//Output today's date.
	const int todayYear {p->tm_year + 1900};
	const int todayMonth {p->tm_mon + 1};
	const int todayDay {p->tm_mday};
	date_print(&todayYear, &todayMonth, &todayDay);
	cout << " is today.\n";

	//Output tomorrow's date.
	int tomorrowYear {todayYear};
	int tomorrowMonth {todayMonth};
	int tomorrowDay {todayDay};
	date_next(&tomorrowYear, &tomorrowMonth, &tomorrowDay);   //Advance one day.
	date_print(&tomorrowYear, &tomorrowMonth, &tomorrowDay);
	cout << " is tomorrow.\n";

	//Output the date of next Christmas, 329 days from today (Jan 30 2025).
	int christmasYear {todayYear};
	int christmasMonth {todayMonth};
	int christmasDay {todayDay};
	date_next(&christmasYear, &christmasMonth, &christmasDay, 329);
	date_print(&christmasYear, &christmasMonth, &christmasDay);
	cout << " is next Christmas.\n";

	return EXIT_SUCCESS;
}

void date_print(const int *pyear, const int *pmonth, const int *pday)
{
	cout << *pmonth << "/" << *pday << "/" << *pyear;
}

void date_next(int *pyear, int *pmonth, int *pday, int n)
{
	for (int i {0}; i < n; ++i) {
		//Call the other next function, the one with 1 argument
		date_next(pyear, pmonth, pday);
	}
}

void date_next(int *pyear, int *pmonth, int *pday)
{
	if (*pday < date_length[*pmonth]) {
		++*pday;             //Increments *pday, not p
	} else {
		*pday = 1;           //Advance into the next month.
		if (*pmonth < 12) {
			++*pmonth;
		} else {
			*pmonth = 1; //Advance into the next year.
			++*pyear;
		}
	}
}