计算任何一天是星期几的C语言源代码.

#include <stdio.h>
int main()
{
int day,mn,yr,i,days=0,s,k;
int mont[13]={0,31,28,31,30,31,30,31,31,30,31,30,31};
char wek[][9]={ {'S','u','n','d','a','y'},
{'M','o','n','d','a','y'},
{'T','u','e','s','d','a','y'},
{'W','e','d','n','s','d','a','y'},
{'T','h','u','r','s','d','a','y'},
{'F','r','i','d','a','y'},
{'S','a','t','u','r','d','a','y'}
      };
printf("Inpute the date (year-month-day):");
scanf("%d-%d-%d",&yr,&mn,&day);
if (yr%4==0||yr%100==0||yr%400==0)
mont[2]=29;
else
mont[2]=28;
for (i=0;i<mn;i++)
days+=mont[i];
days+=day;
s=yr-1+(int)((yr-1)/4)-(int)((yr-1)/100)+(int)((yr-1)/400)+days;
k=s%7;
printf("%d-%d-%d is %s.",yr,mn,day,wek[k]);
   return 0;
}