程序代码：

#include <stdio.h>

struct date {
    int year;
    int month;
    int day;
    int temp;
    char name[9];
};
const struct date week[7]={
        {0,0,0,0,{'S','u','n','d','a','y'}},
        {0,0,0,1,{'M','o','n','d','a','y'}},
        {0,0,0,2,{'T','u','e','s','d','a','y'}},
        {0,0,0,3,{'W','e','d','n','e','s','d','a','y'}},
        {0,0,0,4,{'T','h','u','r','s','d','a','y'}},
        {0,0,0,5,{'F','r','i','d','a','y'}},
        {0,0,0,6,{'S','a','t','u','r','d','a','y'}},
};    
    
int main (void) {

    struct date thedate;

    int getDaysOfDate (struct date d);

    int numberOfWeek,i,j;

    printf ("Enter date [yyyy mm dd]:");
    scanf ("%i %i %i",&thedate.year,&thedate.month,&thedate.day);

    printf ("The day is : ");

    numberOfWeek=(getDaysOfDate(thedate)-621049)%7;

    for(i=0;i<7;i++) {

        if(week[i].temp==numberOfWeek){
            
            for (j=0;j<9;j++){

                printf ("%c",week[i].name[j]);    
            }
        }
    }    

    return 0;

}

int getDaysOfDate (struct date d) {

    int days;

    if(d.month<=2) {

        days=1461*(d.year-1)/4+153*(d.month+13)/5+d.day;

    }else{

        days=1461*d.year/4+153*(d.month+1)/5+d.day;

    }
    
    if(d.year>=1700&&d.month>=3&&d.day>=1 && d.year<=1800&&d.month<=2&&d.day<=28) {

        days=days+2;

    }

    if(d.year>=1800&&d.month>=3&&d.day>=1 && d.year<=1900&&d.month<=2&&d.day<=28) {

        days=days+1;

    }

    return days;

}