日期算星期（使用基姆拉尔森计算公式）

#include <stdio.h>

    
unsigned char CaculateWeekDay(unsigned int y,unsigned char m, unsigned char d)
{
    if(m==1||m==2) {
        m+=12;
        y--;
    }
    return (unsigned char)((d+2*m+3*(m+1)/5+y+y/4-y/100+y/400)%7);    
}    
    
int main () {
    unsigned char day,month;
    unsigned int year;
    day=17;
    month=2;
    year=2022;
    //char w=(days + 2 * month + 3 * (month + 1) / 5 + year + year / 4 - year / 100 + year / 400) % 7;
    char iWeek=CaculateWeekDay(year,month,day);
    switch(iWeek)
    {
    case 0: printf("星期一\n"); break;
    case 1: printf("星期二\n"); break;
    case 2: printf("星期三\n"); break;
    case 3: printf("星期四\n"); break;
    case 4: printf("星期五\n"); break;
    case 5: printf("星期六\n"); break;
    case 6: printf("星期日\n"); break;
    }
    return 0;
}