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How to convert int to Month and Year?

MisterTams (125)
Exactly as the title states, how can I do this?
I have the conversion for the month down.
I cannot figure out how to find the day.
I got it working originally for January and February but March was screwing up.
So If I enter 33 I need to display February 2nd. Enter 363 will be December 29th, etc...


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#ifndef INTTODAY_H
#define INTTODAY_H

class IntToDay
{
private:
	int Day;
public:
	IntToDay (int daynum) 
	{
		Day = daynum;
	};

	void print();


};


#endif



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#include <iostream>
#include <string>
#include <iomanip>
#include "IntToDay.h"
using namespace std;

int main()
{
	int num;
	cout << "Please enter a day of the year: ";
	cin >> num;

	IntToDay convert(num);

	convert.print();




	return 0;
}


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#include <iostream>
#include <iomanip>
#include <string>
#include "IntToDay.h"
using namespace std;

void IntToDay::print()
{
	int x = 1;
	int Jan = 31;
	int Feb = 28 + Jan;
	int Mar = 31 + Feb;
	int Apr = 30 + Mar;
	int May = 31 + Apr;
	int Jun = 30 + May;
	int Jul = 31 + Jun;
	int Aug = 31 + Jul;
	int Sept = 30 + Aug;
	int Oct = 30 + Sept;
	int Nov = 30 + Oct;
	int Dec = 31 + Nov;
	
	int January[31], February[28], March[31], April[30], MayM[31], June[30], July[31];
	int August[31], September[30], October[30], November[30], December[31];

	for (int count = 0; count < 31; count++)
	{
		January[count] = x;
		March[count] = x;
		July[count] = x;
		MayM[count] = x;
		August[count] = x;
		December[count] = x;
		x++;
	}
	for (int count = 0; count < 30; count++)
	{
		April[count] = x;
		June[count] = x;
		September[count] = x;
		October[count] = x;
		November[count] = x;
		x++;
	}
	for (int count = 0; count < 28; count++)
	{
		February[count] = x;
		x++;
	}

	int MonthDays[] = { 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365 };
	int indexOfMonth;
	if (Day >= 1 && Day <= Jan)
	{
		cout << "Month: January" << endl;
		int Temp = MonthDays[0] - Day + 1;
		int indexOfMonth = 31 - Temp;
		cout << "Day: " << January[indexOfMonth] << endl;
	}
	else if (Day > Jan && Day <= Feb) 
	{
		cout << "Month: February" << endl;
		int convert = (MonthDays[1] - Day);
		int Temp = (MonthDays[1] - convert);
		indexOfMonth = 28 - Temp;
		cout << "Day: " << February[indexOfMonth] << endl;
	}
	else if (Day > Feb && Day <= Mar)
	{
		cout << "Month: March" << endl;
		int Temp = (Mar - Day);
		indexOfMonth = Mar - Temp - 3;
		cout << "Day: " << March[indexOfMonth] << endl;
	}
	else if (Day > Mar && Day <= Apr)
	{
		cout << "Month: April" << endl;
		int Temp = (Apr - Day);
		indexOfMonth = Apr - Temp - 1;
		cout << "Day: " << April[indexOfMonth] << endl;
	}
	else if (Day > Apr && Day <= May)
	{
		cout << "Month: May" << endl;
		int Temp = (May - Day);
		indexOfMonth = May - Temp - 1;
		cout << "Day: " << MayM[indexOfMonth] << endl;
	}
	else if (Day > May && Day <= Jun)
	{
		cout << "Month: June" << endl;
		int Temp = (Jun - Day);
		indexOfMonth = Jun - Temp - 1;
		cout << "Day: " << June[indexOfMonth] << endl;
	}
	else if (Day > Jun && Day <= Jul)
	{
		cout << "Month: July" << endl;
		int Temp = (Jul - Day);
		indexOfMonth = Jul - Temp - 1;
		cout << "Day: " << July[indexOfMonth] << endl;
	}
	else if (Day > Jul && Day <= Aug)
	{
		cout << "Month: Aug" << endl;
		int Temp = (Aug - Day);
		indexOfMonth = Aug - Temp - 1;
		cout << "Day: " << August[indexOfMonth] << endl;
	}
	else if (Day > Aug && Day <= Sept)
	{
		cout << "Month: September" << endl;
		int Temp = (Sept - Day);
		indexOfMonth = Sept - Temp - 1;
		cout << "Day: " << September[indexOfMonth] << endl;
	}
	else if (Day > Sept && Day <= Oct)
	{
		cout << "Month: October" << endl;
		int Temp = (Oct - Day);
		indexOfMonth = Oct - Temp - 1;
		cout << "Day: " << October[indexOfMonth] << endl;
	}
	else if (Day > Oct && Day <= Nov)
	{
		cout << "Month: November" << endl;
		int Temp = (Nov - Day);
		indexOfMonth = Nov - Temp - 1;
		cout << "Day: " << November[indexOfMonth] << endl;
	}
	else if (Day > Nov && Day <= Dec)
	{
		cout << "Month: December" << endl;
		int Temp = (Dec - Day);
		indexOfMonth = Dec - Temp - 1;
		cout << "Day: " << December[indexOfMonth] << endl;
	}
}
gunnerfunner (2127)
All months, except feb, have fixed number of days – so we use 3 vectors – one for jan, one for marTodec and one for feb depending on whether or not its a leap year.
Given leap year or not the appropriate vectors are combined (using move instead of copy) to make a year vector and then the day and month are read off using std::find and std::distance – read up these functions and shout if anything's unclear: 
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#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <iterator>

int main()
{
    std::vector<std::string> jan(31, "Jan");
    //for (const auto & elem : jan)std::cout << elem << " ";std::cout << "\n";
    std::cout << "jan size: " << jan.size() << "\n";//sanity checks
    std::vector<std::string> marTodec{306};
    auto itr = marTodec.begin();
    std::fill(marTodec.begin(), itr + 31, "Mar");
    itr += 31;
    std::fill(itr, itr + 30, "Apr");
    itr += 30;
    std::fill(itr, itr+31, "May");
    itr += 31;
    std::fill(itr, itr+30, "Jun");
    itr += 30;
    std::fill(itr, itr+31, "Jul");
    itr += 31;
    std::fill(itr, itr+31, "Aug");
    itr += 31;
    std::fill(itr, itr+30, "Sep");
    itr += 30;
    std::fill(itr, itr + 31, "Oct");
    itr += 31;
    std::fill(itr, itr+30, "Nov");
    itr+= 30;
    std::fill(itr, itr+31, "Dec");
   // for (const auto& elem : marTodec) std::cout << elem << " ";std::cout << "\n";
    std::cout << "marTodec size: " << marTodec.size() << "\n";
    bool leap = true;
    if(leap)
    {
        std::vector<std::string> feb(29, "feb");
       // std::cout << "feb size: " << feb.size() << "\n";
        std::vector<std::string> year {};
        year.reserve(jan.size() + feb.size() + marTodec.size());
        year.insert(year.end(), std::make_move_iterator(jan.begin()), std::make_move_iterator(jan.end()));
        year.insert(year.end(), std::make_move_iterator(feb.begin()), std::make_move_iterator(feb.end()));
        year.insert(year.end(), std::make_move_iterator(marTodec.begin()), std::make_move_iterator(marTodec.end()));
        std::cout << "year size: " << year.size() << "\n";
        //for (const auto& elem : year)std::cout << elem << " "; std::cout << "\n";

        std::cout << "Enter day of the year \n";
        size_t day{};
        std::cin >> day;
        auto itrMonth = std::find(year.begin(), year.end(), year[day-1]);
        auto itrDay = year.begin() + day;

        std::cout << "The day is: " << year[day - 1] << " " << std::distance(itrMonth, itrDay);
    }
    else
    {
        std::vector<std::string> feb(28, "feb");
       // std::cout << "feb size: " << feb.size() << "\n";
        std::vector<std::string> year {};
        year.reserve(jan.size() + feb.size() + marTodec.size());
        year.insert(year.end(), std::make_move_iterator(jan.begin()), std::make_move_iterator(jan.end()));
        year.insert(year.end(), std::make_move_iterator(feb.begin()), std::make_move_iterator(feb.end()));
        year.insert(year.end(), std::make_move_iterator(marTodec.begin()), std::make_move_iterator(marTodec.end()));
        std::cout << "year size: " << year.size() << "\n";
        //for (const auto& elem : year)std::cout << elem << " "; std::cout << "\n";

        std::cout << "Enter day of the year \n";
        size_t day{};
        std::cin >> day;
        auto itrMonth = std::find(year.begin(), year.end(), year[day-1]);
        auto itrDay = year.begin() + day;

        std::cout << "The day is: " << year[day - 1] << " " << std::distance(itrMonth, itrDay);
     }
}
JLBorges (13770)
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#include <iostream>
#include <string>

int main()
{
    enum { JAN = 1, FEB = 2, DEC = 12 };

    // cumulative_days[0] == 0 is a place holder; does not correspond to an actual month
    int cumulative_days[DEC+1] = { 0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 } ;
    // add up the days to make it cumulative
    for( int i = JAN ; i <= DEC ; ++i ) cumulative_days[i] += cumulative_days[i-1] ;

    // JAN == 1, DEC == 12, month_name[0] is unused
    const std::string month_name[DEC+1] = { "", "Jan", "Feb", "Mar", "Apr", "May", "Jun",
                                            "Jul", "Aug", "Sep", "Oct", "Nov", "Dec" } ;
    int nday ;
    std::cout << "day of year? " ;
    std::cin >> nday ;

    if( nday > cumulative_days[FEB] ) // if it is later than 28 FEB
    {
        char leap ; // we need to know if it is a leap year
        std::cout << "is it a leap year (y/n)? " ;
        std::cin >> leap ;

        if( leap == 'y' || leap == 'Y' ) // add one to FEB onwards for leap year
            for( int i = FEB ; i <= DEC ; ++i ) ++cumulative_days[i] ;
    }

    if( nday > 0 && nday <= cumulative_days[DEC] ) // if valid
    {
        int month = JAN ;
        while( nday > cumulative_days[month] ) ++month ; // get to the right month

        // print out the name of the month and the day in the month
        std::cout << month_name[month] << ' ' << nday - cumulative_days[month-1] << '\n' ;
    }
}
JLBorges (13770)
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#include <iostream>
#include <ctime>
#include <iomanip>

int main()
{
    const auto now = std::time(nullptr) ;
    std::tm tm = *std::localtime( std::addressof(now) ) ;

    int nday ;
    std::cout << "days since january 01, " << 1900+tm.tm_year << ": " ;
    std::cin >> nday ;

    tm.tm_mon = 0 ; // january
    tm.tm_mday = nday ;
    tm.tm_hour = 12 ; // noon

    const auto t_nday = std::mktime( std::addressof(tm) ) ;
    std::cout << std::put_time( std::localtime( std::addressof(t_nday) ), "%d %B, %Y\n" ) ;
}
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