c语言 输出一个日期是该年的第几天

这个版本逻辑相对清晰，错误输入的判断十分完整；

#include <stdio.h>
/*******tonytrek 2021.7.17**********/
//input date,out put the count of the day from the begain of that year
int data_cal(int,int,int);
int main()
{
    int year=2012,month=2,date=29;
    int ret=data_cal(year,month,date);
    printf("ret=%d\n",ret);
    return 0;
}
int data_cal(int year,int month,int date)
{
int data_list[12]={31,28,31,30,31,30,31,31,30,31,30,31};
int iter,cal;
if(0==year%400||(0!=year%100&&0==year%4)) //first level data exception
    data_list[1]+=1;
if(year<1000||year>4000||month>12||month<0||date<0) //second level data exception
{
    printf("bad inpute date\n");
    return -1;
}
if(date>data_list[month-1])
{
    printf("bad data\n");
    return -1;
}
for(iter=0;iter<month-1;iter++)
{
    cal+=data_list[iter];
}
cal+=date;
return cal;
}