C++: Calendar

#include <windows.h>
#include <iostream>

//--------------------------------------------------------------------------------------------------
using namespace std;


//--------------------------------------------------------------------------------------------------
class calender
{
public:
	void drawCalender( int y )
	{
		year = y;
		for( int i = 0; i < 12; i++ )
		firstdays[i] = getfirstday( i );

		isleapyear();
		build();
	}

private:
	void isleapyear()
	{
		isleap = false;

		if( !( year % 4 ) )
		{
			if( year % 100 ) isleap = true;
			else if( !( year % 400 ) ) isleap = true;
		}
	}

	int getfirstday( int m )
	{
		int y = year;

		int f = y + 1 + 3 * m - 1;
		m++;
		if( m < 3 ) y--;
		else f -= int( .4 * m + 2.3 );

		f += int( y / 4 ) - int( ( y / 100 + 1 ) * 0.75 );
		f %= 7;

		return f;
	}

	void build()
	{
		int days[] = { 31, isleap ? 29 : 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
		int lc = 0, lco = 0, ystr = 7, start = 2, fd = 0, m = 0;
		HANDLE h = GetStdHandle( STD_OUTPUT_HANDLE );
		COORD pos = { 0, ystr };
		draw();

		for( int i = 0; i < 4; i++ )
		{
			for( int j = 0; j < 3; j++ )
			{
				int d = firstdays[fd++], dm = days[m++];
				pos.X = d * 3 + start;
				SetConsoleCursorPosition( h, pos );

				for( int dd = 0; dd < dm; dd++ )
				{
					if( dd < 9 ) cout << 0 << dd + 1 << " ";
					else cout << dd + 1 << " ";

					pos.X += 3;
					if( pos.X - start > 20 )
					{
						pos.X = start; pos.Y++;
						SetConsoleCursorPosition( h, pos );
					}
				}

				start += 23;
				pos.X = start; pos.Y = ystr;
				SetConsoleCursorPosition( h, pos );
			}
			ystr += 9; start = 2;
			pos.Y = ystr;
		}
	}

	void draw()
	{
		system( "cls" );
		cout << "+--------------------------------------------------------------------+" << endl;
		cout << "|                              [SNOOPY]                              |" << endl;
		cout << "|                                                                    |" << endl;
		cout << "|                             == " << year << " ==                             |" << endl;
		cout << "+----------------------+----------------------+----------------------+" << endl;
		cout << "|       JANUARY        |       FEBRUARY       |         MARCH        |" << endl;
		cout << "| SU MO TU WE TH FR SA | SU MO TU WE TH FR SA | SU MO TU WE TH FR SA |" << endl;
		cout << "|                      |                      |                      |" << endl;
		cout << "|                      |                      |                      |" << endl;
		cout << "|                      |                      |                      |" << endl;
		cout << "|                      |                      |                      |" << endl;
		cout << "|                      |                      |                      |" << endl;
		cout << "|                      |                      |                      |" << endl;
		cout << "+----------------------+----------------------+----------------------+" << endl;
		cout << "|        APRIL         |          MAY         |         JUNE         |" << endl;
		cout << "| SU MO TU WE TH FR SA | SU MO TU WE TH FR SA | SU MO TU WE TH FR SA |" << endl;
		cout << "|                      |                      |                      |" << endl;
		cout << "|                      |                      |                      |" << endl;
		cout << "|                      |                      |                      |" << endl;
		cout << "|                      |                      |                      |" << endl;
		cout << "|                      |                      |                      |" << endl;
		cout << "|                      |                      |                      |" << endl;
		cout << "+----------------------+----------------------+----------------------+" << endl;
		cout << "|         JULY         |        AUGUST        |       SEPTEMBER      |" << endl;
		cout << "| SU MO TU WE TH FR SA | SU MO TU WE TH FR SA | SU MO TU WE TH FR SA |" << endl;
		cout << "|                      |                      |                      |" << endl;
		cout << "|                      |                      |                      |" << endl;
		cout << "|                      |                      |                      |" << endl;
		cout << "|                      |                      |                      |" << endl;
		cout << "|                      |                      |                      |" << endl;
		cout << "|                      |                      |                      |" << endl;
		cout << "+----------------------+----------------------+----------------------+" << endl;
		cout << "|        OCTOBER       |       NOVEMBER       |       DECEMBER       |" << endl;
		cout << "| SU MO TU WE TH FR SA | SU MO TU WE TH FR SA | SU MO TU WE TH FR SA |" << endl;
		cout << "|                      |                      |                      |" << endl;
		cout << "|                      |                      |                      |" << endl;
		cout << "|                      |                      |                      |" << endl;
		cout << "|                      |                      |                      |" << endl;
		cout << "|                      |                      |                      |" << endl;
		cout << "|                      |                      |                      |" << endl;
		cout << "+----------------------+----------------------+----------------------+" << endl;
	}

	int firstdays[12], year;
	bool isleap;
};
//--------------------------------------------------------------------------------------------------
int main( int argc, char* argv[] )
{
	int y;
	calender cal;

	while( true )
	{
		system( "cls" );
		cout << "Enter the year( yyyy ) --- ( 0 to quit ): "; 
		cin >> y;
		if( !y ) return 0;

		cal.drawCalender( y );
		cout << endl << endl << endl << endl << endl << endl << endl << endl;

		system( "pause" );
	}
	return 0;
}
//--------------------------------------------------------------------------------------------------