Program Date Of Birth Counter in C/C++

#include<stdio.h>
#include<stdlib.h>
#include<conio.h>
main()
{
 clrscr();
 int d,m,y,year,month,day,i,n;
 printf("Enter how many times you want to run this program : ");
 scanf("%d",&n);
 for(i=1;i<=n;i++)
 {
 printf("Enter the date : ");
 scanf("%d%d%d",&d,&m,&y);
 if( d>31 || m>12 || (y>1900 || y<=2000) )
 {
 printf("INVALID INPUT");
 getch();
 exit(0);
 }
 year = y-1900;
 year = year/4;
 year = year+y-1900;
 switch(m)
 {
 case 1:
 case 10:
 month = 1;
 break;
 case 2:
 case 3:
 case 11: month = 4;
break;
 case 7:
 case 4:
 month = 0;
break;
 case 5:
 month = 2;
 break;
 case 6:
 month = 5;
 break;
 case 8:
 month = 3;
 break;
 case 9:
 case 12:
 month = 6;
 break;
 }
 year = year+month;
 year = year+d;
 day = year%7;
 switch(day)
 {
 case 0:
 printf("Day was SATURDAY");
break;
 case 1:
 printf("Day was SUNDAY");
break;
 case 2:
 printf("Day was MONDAY");
break;
 case 3: printf("Day was TUESDAY");
break;
 case 4:
printf("Day was WEDNESDAY");
break;
 case 5:
printf("Day was THURSDAY");
break;
 case 6:
 printf("Day was FRIDAY");
 break;
 }
}
 getch();
 return 0;
}