来到地球多久啦

#include <stdio.h>
int leap(int year);                         //闰年返回1，否则返回0
int yeardays(int year, int month, int day); //返回一年中的第几天
int days(int year);                         //返回一年的总天数
int main(void)
{
    int birth_year, birth_month, birth_day;
    int to_year, to_month, to_day;
    int day_num = 0;
    scanf("%d %d %d", &birth_year, &birth_month, &birth_day);
    scanf("%d %d %d", &to_year, &to_month, &to_day);

    if (birth_year == to_year)
    {
        day_num = yeardays(to_year, to_month, to_day) - yeardays(birth_year, birth_month, birth_day);
    }
    else
    {
        day_num = days(birth_year) - yeardays(birth_year, birth_month, birth_day) + 1;
        for (int i = birth_year + 1; i < to_year; i++)
        {
            day_num = day_num + days(i);
        }
        day_num = day_num + yeardays(to_year, to_month, to_day);
    }

    printf("%d
", day_num);

    return 0;
}
int leap(int year)
{
    int ret;

    if ((year % 4 == 0 && year % 100 != 0) || (year % 400 == 0))
    {
        ret = 1;
    }
    else
    {
        ret = 0;
    }

    return ret;
}
int yeardays(int year, int month, int day)
{
    int days = 0;
    int month_days[2][13] = {
        {0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31},
        {0, 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31},
    };
    for (int i = 1; i < month; i++)
    {
        days = days + month_days[leap(year)][i];
    }
    days = days + day;

    return days;
}
int days(int year)
{
    int ret;
    if (leap(year))
    {
        ret = 366;
    }
    else
    {
        ret = 365;
    }

    return ret;
}

输入两个日期（年 月 日），计算两个日期经过了多少天。

可以输入自己的生日和当前的日期，计算自己来到地球多少天了。