timelib.c

/**
* Author: Alexander Kötter
* Date: 2020-02-11
* Edit: 2020-02-25
**/


#include <stdio.h>
#include <stdlib.h>

 int weekday(year)
 {
 int w = (1 + 5*((year-1)%4) +4*((year-1)%100) + 6*((year-1)%400))%7;
 return w;
 }


int is_leapyear(int year)
 {
          if (year > 2400 ||year < 1582)
    {
        return -1;
    }
     if (year % 4 == 0 ||year % 400 == 0)
    {
        return 1;
    }
     if (year % 100)
    {
        return 1;
    }

 }

 int get_days_for_month(int month, int year)
 {

     int days[12] = {1,-2,1,0,1,0,1,1,0,1,0,1};
 if (month >0 && month <13){
    int days_month = 30 + days[month-1] + is_leapyear(year);
 return days_month;
 }
 else {return -1;}
 }

int exists_date(int day,int month, int year)
 {
     if((day >0 &&day <= get_days_for_month(month,year)) && month > 0 && month < 13 && year >= 1582 && year <= 2400)
    {
        return 1;
    }
    else {return -1;}
 }

void input_date(int *day, int *month, int *year)
{
    do
    {
        printf("Input date: ");
        scanf("%i", day);
        fflush(stdin);
        printf("Input month: ");
        scanf("%i", month);
        fflush(stdin);
        printf("Input year: ");
        scanf("%i", year);
        fflush(stdin);
    }
    while (exists_date(*day, *month, *year) != 1);
}


int day_of_the_year(int day,int month, int year)
 {
   // int x=0;
      int tage[12] = {0,1,-1,0,0,1,1,2,3,3,4,4};
      int exists = exists_date(day, month, year);
      int lyear = is_leapyear(year);
      int day_of_year;

      if(exists = 1)
      {
          if (month < 3)
          {
            day_of_year = (month - 1) * 30 + day + tage[(month-1)];
          }
          else
          {
           day_of_year = (month - 1) * 30 + day + tage[(month-1)] + lyear;
          }
           return day_of_year;
      }
      else
      {
          return -1;
      }
 }