[C] Errore "Syntax error & implicit declaration of function"

[Zorgatone]

Salve a tutti ho un problema a compilare il seguente codice (file date.c) in gcc.
Allego anche l'errore che ho ottenuto.

date.c: In function 'main':
date.c:7: warning: implicit declaration of function 'printf'
date.c:8: warning: implicit declaration of function 'scanf'
date.c:12: error: syntax error before "case"

/* Stampa la data nel formato legale */

int main(void)
{
     int month, day, year;

     printf("Enter date (mm/dd/yy): ");
     scanf("%d /%d /%d", &month, &day, &year);

     printf("Dated this %d", day);
     switch (day) {
            case 1: case 21 case 31:
                 printf("st"); break;
            case 2: case 22:
                 printf("nd"); break;
            case 3: case 23:
                 printf("rd"); break;
            default: printf("th"); break;
     }
     printf(" day of ");
          switch (month) {
            case 1: printf("January"); break;
            case 2: printf("February"); break;
            case 3: printf("March"); break;
            case 4: printf("April"); break;
            case 5: printf("May"); break;
            case 6: printf("June"); break;
            case 7: printf("July"); break;
            case 8: printf("August"); break;
            case 9: printf("September"); break;
            case 10: printf("October"); break;
            case 11: printf("November"); break;
            case 12: printf("December"); break;
     }     printf(", 20%.2d.\n", year);
     return 0;
}

Mi potreste aiutare a risolverlo? Grazie