Calender Program in C Programming Language : Display Day of the month

Calender Program in C Programming Language :

Program will accept Year,Month and Date from the user and will display the day of the month.

#include<stdio.h>
#include<conio.h>
#include<math.h>

int isdatevalid(int month, int day, int year)
{
  if (day <= 0) return 0 ;
  switch( month )
    {
      case 1:
      case 3:
      case 5:
      case 7:
      case 8:
      case 10:
      case 12: if (day > 31) return 0 ; else return 1 ;
      case 4:
      case 6:
      case 9:
      case 11: if (day > 30) return 0 ; else return 1 ;
      case 2:
        if ( day > 29 ) return 0 ;
        if ( day < 29 ) return 1 ;

    else return 0 ;
    }
  return 0 ;
}
//------------------------------------------------
int fm(int date, int month,int year)
{
int fmonth,leap;

//leap function 1 for leap & 0 for non-leap

if((year%100==0) && (year%400!=0))
    leap=0;
else if(year%4==0)
    leap=1;
else
    leap=0;

fmonth=3+(2-leap)*((month+2)/(2*month))+(5*month+month/9)/2;
//f(m) formula

fmonth = fmonth % 7; //bring it in range of 0 to 6

return fmonth;
}

//----------------------------------------------
int day_of_week(int date, int month, int year)
{
int dow; //day of week

int YY = year % 100;
int century = year / 100;

printf("nDate: %d/%d/%dnn",date,month,year);

dow = 1.25 *  YY + fm(date,month,year) + date - 2*( century % 4);
//function of weekday for Gregorian

dow = dow % 7; //remainder on division by 7

switch (dow)
    {
    case 0:
        printf("weekday = Saturday");
        break;
    case 1:
        printf("weekday = Sunday");
        break;
    case 2:
        printf("weekday = Monday");
        break;
    case 3:
        printf("weekday = Tuesday");
        break;
    case 4:
        printf("weekday = Wednesday");
        break;
    case 5:
        printf("weekday = Thursday");
        break;
    case 6:
        printf("weekday = Friday");
        break;
    default:
        printf("Incorrect data");
    }
return 0;
}
//------------------------------------------
void main()
{
int date,month,year;
clrscr();

printf("Enter the year ");
scanf("%d",&year);

printf("Enter the month ");
scanf("%d",&month);

printf("Enter the date ");
scanf("%d",&date);

day_of_week(date,month,year);

getch();
}

Output :

Enter the year 2012
Enter the month 02
Enter the date 29

Date: 29/2/2012

weekday = Wednesday