What am I doing wrong?

I am new to C++. I have CodeWarrior, if that makes a difference. I can get this project to compile and receive input. But when it is suppose to output the weekday at the end of "entered is:", I only get "." What am I doing wrong? I have done the formulas manually, they all seem to work. Any help will be greatly appreciated.



//Project 4 - receives the number of a month, the day
//of a month, and a year, and returns the name of the
//day of the week on which that date fell or will fall

#include <iostream> // cin, cout
#include <iomanip> // math library
#include <string> // string library

using namespace std; // introduces namespace std

string DayoftheWeek(string, int, int, int, int, int, int, int, int, int, int, int, int);
//prototype

int main(void)
{
int mon, day, year;
char YorN;
string WeekDay;
do
{
cout << "Enter the number of the month:";
cin >> mon; //month of year
cout << "Enter day of the month:";
cin >> day; //day of month
cout << "Enter the year:";
cin >> year; //year number

cout << "The day of the week for the date you have entered is: ";

string DayoftheWeek(WeekDay); //function call
cout << WeekDay;
cout << ".\n";
cout << "\n\n\nEnter Y to try another, N to stop.\n\t\t";
cin >> YorN;
}
while(YorN=='Y'||YorN=='y');

return 0;
}

string DayoftheWeek(string WeekDay, int mon, int a, int b, int c, int d, int w, int x, int y, int z, int r, int day, int year)
//definition of function to find day of week
{
a = mon;
b = day;
c = year % 100;
d = year / 100;

if(a <= 2)
{
a += 10;
}
else
{
a -= 2;
}
{
w = (13 * a - 1) / a;
x = c / 4;
y = d / 4;
z = w + x + y + b + c - 2 * d;
r = z % 7;
}
switch(r)//for remainder
{
case 0: WeekDay = "Sunday";

case 1: WeekDay = "Monday";

case 2: WeekDay = "Tuesday";

case 3: WeekDay = "Wednesday";

case 4: WeekDay = "Thursday";

case 5: WeekDay = "Friday";

default: WeekDay = "Saturday";

}return WeekDay;

}

you only have to pass the variables you'll need in the function. not the ones you use to calculate stuff(like x,w,y,...)
and when you return a value from your function you don't have to put it in your arg list, do it like this: return_value=function(arg1,arg2);
and when u use switch(), make sure you add break; after every case. otherwise he will always take the default value.

Are you sure the formula for calculating the day is right? Because I entered my birthday and it came up with sunday, and I was born on a wednesday. I could be wrong, it was so long ago, and I was still very young. Or it could be the millenium bug

well here's the code:

Code:

#include <iostream> // cin, cout 
#include <iomanip> // math library 
#include <string> // string library 

using namespace std; // introduces namespace std 

string DayoftheWeek(int , int , int ); 
//prototype 

int main(void) 
{ 
int mon, day, year; 
char YorN; 
string WeekDay; 
do 
{ 
cout << "Enter the number of the month:"; 
cin >> mon; //month of year 
cout << "Enter day of the month:"; 
cin >> day; //day of month 
cout << "Enter the year:"; 
cin >> year; //year number 

cout << "The day of the week for the date you have entered is: "; 

WeekDay = DayoftheWeek(mon,day,year); //function call 
cout << WeekDay; 
cout << ".\n"; 
cout << "\n\n\nEnter Y to try another, N to stop.\n\t\t"; 
cin >> YorN; 
} 
while(YorN=='Y'||YorN=='y'); 

return 0; 
} 

string DayoftheWeek(int a,int b, int year) 
//definition of function to find day of week 
{ 
string WeekDay;
int c,d,w,x,y,z,r;
c = year % 100; 
d = year / 100; 

if(a <= 2) 
{ 
a += 10; 
} 
else 
{ 
a -= 2; 
} 
{ 
w = (13 * a - 1) / a; 
x = c / 4; 
y = d / 4; 
z = w + x + y + b + c - 2 * d; 
r = z % 7; 
} 
switch(r)//for remainder 
{ 
case 0: WeekDay = "Sunday"; 
	break;
case 1: WeekDay = "Monday"; 
	break;
case 2: WeekDay = "Tuesday"; 
	break;
case 3: WeekDay = "Wednesday"; 
	break;
case 4: WeekDay = "Thursday"; 
	break;
case 5: WeekDay = "Friday"; 
	break;
default: WeekDay = "Saturday"; 
	break;
}return WeekDay; 
}

That function to me looks like a poor attempt at zellers algorithm. Here is how to write that function properly..... adapt it yourself if you want it to return a string instead of an int....

Code:

int calender::whatdayisfirstofmonth()
{
	int c=year/100; // # of centuries
	int d=year%100; // # of years through century
	int m=(month+10)%12; // # of month march is 1,feb is 12
	int k=1; // set the day part to 1 so we get back the day for first of month
	if ((month==1)||(month==2))// treat jan and feb as if they were in previous year
	{
		if (d==0) // if d is 0 then to go back a year d becomes 99 and c become c-1
		{
			d=99;
			c-=1;
		}
		else
		{
		d-=1; // jan and feb are treated as previous year
		}
	}
	 float g=(k + (floor(((13*m)-1)/5)) + d + (floor(d/4)) + (floor(c/4)) - (2*c));
	 int f=static_cast<int>(g)%7; // cast result of algorithm to int to take modulus
	 if (f<0) // if negative add 7

	 {
		 f+=7;
	 }
	 return f; // returns 0 to 6 corresponding to sunday to saturday
}