Zeller #2

/*Programa: Congruencia De Zeller
  Realizado Por: Jorge Chayan*/
#include <stdio.h>

int zeller(int , int, int);

int main()
{
    int meses[13] = {0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
    char *dia_sem;
    int mes;
    int dia;
    int anio;
    int res;
    do
    {
        printf ("\nDia: ");
        scanf ("%d", &dia);
        printf ("\nMes: ");
        scanf ("%d", &mes);
        if (dia > meses[mes]) printf ("\nError En El Mes Seleccionado No Existe Tal Dia\n");
        if (dia < 1) printf ("\nError! Dia 0 no Existe!\n");
        if (mes < 1 || mes > 12) printf ("\nError. Rango De Mes: 1-12\n");
    }while (dia > meses[mes] || dia < 1 || mes < 1 || mes > 12);

    printf ("\nA\244o: ");
    scanf ("%d", &anio);
    if (mes < 3) anio = anio - 1;
    res = zeller(anio, mes, dia);
    switch (res)
    {
         case 0:
                dia_sem = "Domingo";
                break;
         case 1:
                dia_sem = "Lunes";
                break;
         case 2:
                dia_sem = "Martes";
                break;
         case 3:
                dia_sem = "Miercoles";
                break;
         case 4:
                dia_sem = "Jueves";
                break;
         case 5:
                dia_sem = "Viernes";
                break;
         case 6:
                dia_sem = "Sabado";
                break;
    }

    printf ("\nLa Fecha Corresponde Con Un %s", dia_sem);
    getchar();
    getchar();
    return 0;
}

int zeller(int y, int m, int d)
{
    int t[12] = {0, 3, 2, 5, 0, 3, 5, 1, 4, 6, 2, 4};
    return (y + (y / 4) - (y / 100) + (y / 400) + t[m-1] + d) % 7;
}