用C++编写万年历系统

非常感谢您的提问！以下是一个简单的 C 代码，可以实现万年历系统：

#include <stdio.h>

int main()
{
    int year, month, day, days, i, j;
    int month_days[12] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
    char week[7][4] = {"Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"};

    printf("Please enter the year: ");
    scanf("%d", &year);
    printf("Please enter the month: ");
    scanf("%d", &month);

    if ((year % 4 == 0 && year % 100 != 0) || year % 400 == 0)
    {
        month_days[1] = 29;
    }

    days = 0;
    for (i = 0; i < month - 1; i++)
    {
        days += month_days[i];
    }

    days += 1;
    day = 1;

    printf("\n     %d年%d月\n", year, month);
    printf("--------------------\n");
    for (i = 0; i < 7; i++)
    {
        printf("%s ", week[i]);
    }
    printf("\n");

    for (i = 0; i < days % 7; i++)
    {
        printf("    ");
    }

    for (j = 1; j <= month_days[month - 1]; j++)
    {
        printf("%2d  ", j);
        if ((days + j) % 7 == 0)
        {
            printf("\n");
        }
    }

    printf("\n");

    return 0;
}

这个程序可以根据用户输入的年份和月份，输出该月的日历。程序中使用了一个月份天数的数组和一个星期几的数组，以及一些简单的循环和判断语句。