# C > Mathematics Code Examples

## Program to find your Day of Birth given Date of Birth

``` Program to find your Day of Birth given Date of Birth #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 is SATURDAY "); break; case 1: printf(" Day is SUNDAY "); break; case 2: printf(" Day is MONDAY "); break; case 3: printf(" Day is TUESDAY "); break; case 4: printf(" Day is WEDNESDAY "); break; case 5: printf(" Day is THURSDAY "); break; case 6: printf(" Day is FRIDAY "); break; } } getch(); return 0; } ```