Calendar ALMOST DONE!!!

Howdie all.

Up front I'd like to thank your for taking the time to read this.
Here is my problem , I wrote a program that takes the date entered as MMDDYYYY, and it converts it to for example

01012000 to January 1, 2000..

Here is my problem when I type in the about input 01012000 I get January 20 2000...I know its a math error, but for the life of me I cannot find it...any help would be appreciated.

Oh and there is one more thing , If at all you could give suggestions on how to shorten the code, i would be very grateful, thanks again. Heres the code

Code:

#include <iostream>
#include <iomanip>
#include <string>
using namespace std;

void input();
bool checkdigit();
bool checklength();
bool checkday();
bool checkmonth();
int contoint();
int contointd();
int contointy();
void printdate();

int n,a,b,c;
string date, stop, day, year, month;
bool ok;

int main()
{
	input();

	while (date != "stop")
	{
		ok = checklength();
		if (ok == true)
			ok = checkdigit();
		if (ok == true)
		{
			month = date.substr (0,2);
			day = date.substr (2,2);
			year = date.substr (4,4);
			a = contoint();
			b = contointd();
			c = contointy();
			ok = checkmonth();
			if (ok = true)
			{
				ok = checkday();
				if (ok == true)
					printdate();
			}
		}

		input();
	}
	return 0;
}

void input()
{
	cout << endl<< "Enter Stop to quit" << endl << "Enter the date in the form of MMDDYYYY or MDDYYY :";
		cin >> date;
}

bool checklength()
{
	if (date.length() == 7)
		date = "0" + date;
	if (date.length() != 8)
	{
		cout << "Your Lenght is wrong" << endl;
		return false;
	}
	
	return true;
}

bool checkdigit()
{
	n = 0;
	while (n <=7)
	{
		if (date[n] >= 48 && date[n] <= 57)
			n++;
		else n = 50;
			if(n == 50 || n == 0)
			{
				cout << "Use all numbers"<< endl;
				return false;
			}
	}
	return true;
}

int contoint()
{
	int a = 0, x = 0;
	int len = month.length();
	while (x < len)
	{
		a = a * 10 + int (month[x]) - 48;
		x++;
	}
	return a;
}

int contointd()
{
	int b = 0, x=0;
	int len = day.length();
	while (x < len)
	{ b=b * 10 + int (year[x]) - 48;
	x++;
	}
	return  b;
}

int contointy()
{ 
	int c = 0, x = 0;
	int len = year.length();
	while (x < len)
	{ 
		c = c * 10 + int ( year [x]) - 48;
		x++ ;
	}
	return c;
}

bool checkmonth()
{ 
	if (a == 0 || a > 12)
	{ 
		cout << "Month is Bad."<< endl;
		return false;
	}
		return true;
}

bool checkday()
{
	if (b == 0 || b > 31)
	{
		cout<<" Day is Bad." << endl;
		return false;
	}
	if (a == 2 && b == 29)
	{
		if (c % 400 == 0)
			return true;
		else if (c % 100 == 0)
		{
			cout << " Day is not correct." << endl;
			return false;
		}
		else if ( c % 4 == 0 )
			return true;
		else 
		{
			cout << "The day is not correct." << endl;
			return false;
		}
	}
	if (a == 4 || a == 6 || a == 9 || a == 11)
	{ 
		if (b > 30) 
		{
			cout << " Day is bad." << endl;
			return false;
		}
	}
	return true;
}
	void printdate()
	{
		if (a == 1)
			cout <<" January";
		else if (a == 2)
			cout << "February";
		else if (a == 3)
			cout << "March";
		else if (a == 4)
			cout << "April";
		else if (a == 5) 
			cout << "May";
		else if (a == 6)
			cout << "June";
		else if (a == 7)
			cout << "July";
		else if (a == 8)
			cout << "August";
		else if (a == 9) 
			cout << "September";
		else if (a == 10) 
			cout << "October";
		else if (a == 11)
			cout << "November";
		else if (a == 12)
			cout << "December";
		cout << b<<" ,  " << c<< endl;
	}

Right here:

Code:

int contointd()
{
	int b = 0, x=0;
	int len = day.length();
	while (x < len)
	{ b=b * 10 + int (year[x]) - 48;
	x++;
	}
	return  b;
}

That should be day[x]

> int contoint();
> int contointd();
> int contointy();
> void printdate();
Pass some parameters to these functions
Then you can get rid of all your global variables.

> int n,a,b,c;
And while you're at it, give them better names.

> if (ok = true)
1. you meant ==
2. since it is a boolean, you should just say either

Code:

if ( ok ) // its all good
if ( !ok ) // its all bad

In fact you can reduce the whole thing to

Code:

if ( checkmonth() && checkday() ) printdate();

> if (date[n] >= 48 && date[n] <= 57)
Don't assume you're using the ASCII character set
if (date[n] >= '0' && date[n] <= '9')
is both more readable and more portable

> a = a * 10 + int (month[x]) - 48;
Basically the same code in 3 different functions
With some parameters, you could so easily make all 3 the same function.

> if (a == 1)
> cout <<" January";
Use an array

Code:

static char *months[] = { "January", .... };
cout << months[a-1];