gregorian_to_jalali.c

/*
 * Language: C
 * Date: 2021/12/30
 * Name: gregorian_to_jalali.c
 * Repository: https://github.com/BaseMax/gregorian_to_jalali
 */

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

typedef struct {
    int year;
    int month;
    int day;
} date_struct;

date_struct gregorian_to_jalali(int year, int month, int day)
{
	date_struct result;
	int array[] = {0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334};

	if(year <= 1600) {
		year -= 621;
		result.year = 0;
	} else {
		year -= 1600;
		result.year = 979;
	}

	int temp = (year > 2) ? (year + 1) : year;
	int days = ((int)((temp + 3) / 4)) + (365 * year) - ((int)((temp + 99) / 100)) - 80 + array[month - 1] + ((int)((temp + 399) / 400)) + day;
	result.year += 33 * ((int)(days / 12053));
	days %= 12053;
	result.year += 4 * ((int)(days / 1461));
	days %= 1461;

	if(days > 365){
		result.year += (int)((days - 1) / 365);
		days = (days-1) % 365;
	}

	result.month = (days < 186)
							? 1 + (int)(days / 31)
							: 7 + (int)((days - 186) / 30);

	result.day = 1 + ((days < 186)
							? (days % 31)
							: ((days - 186) % 30));

	return result;
}

char* gregorian_to_jalali_str(int year, int month, int day)
{
	char* buffer = malloc(sizeof(char) * 10);
	date_struct result = gregorian_to_jalali(year, month, day);
	
	sprintf(buffer, "%04d/%02d/%02d", result.year, result.month, result.day);
	return buffer;
}