Naive implementation of Unix Timestamp to DateTime conversion

unixtime.c

typedef struct _DateTime {
	uint16_t year;
	uint8_t month;
	uint8_t day;
	uint8_t hour;
	uint8_t minute;
	uint8_t second;
} DateTime;

uint8_t monthDays[] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};

void datetime_update(uint32_t time, DateTime* dt) {
	uint32_t days = (time / 86400);

	dt->year = 1970;
	dt->month = 1;
	dt->day = 1;

	while(1) { // rewrite this!
		char leap_year = (dt->year % 4) == 0;

		for(int i = 0; i < 12 ;i++) {
			uint8_t days_in_month = monthDays[i];

			if(i == 1 && leap_year) { // February of leap year
				days_in_month++;
			}

			if(days < days_in_month) {
				dt->day = days + 1;
				days = 0;
				break;
			}

			days -= days_in_month;

			dt->month++;
		}

		if(days == 0) {
			break;
		}

		dt->month = 1;
		dt->year++;
	}

	uint32_t seconds = (time % 86400);

	dt->hour = seconds / 3600;
	dt->minute = (seconds % 3600) / 60;
	dt->second = (seconds % 3600) % 60;
}

int main() {
	init_hw();

	PWR_BackupAccessCmd(ENABLE); // ugly ass construction. Time counter is write protected.
	RTC_WaitForLastTask();
	RTC_SetCounter(1375982740);
	RTC_WaitForLastTask();
	PWR_BackupAccessCmd(DISABLE);

	DateTime dt;

	while(1) {
		uint32_t time = RTC_GetCounter(); // unix timestamp

		datetime_update(time, &dt);

		printf("Time is %d - %d/%02d/%02d %02d:%02d:%02d!\n", time, dt.year, dt.month, dt.day, dt.hour, dt.minute, dt.second);

		delay_ms(1000);
	}
}

I have checked this code. Not working properly.
I gave this 1622472218 timestamp. The converted result is : 14:43:38 2-4-2026 but it should be 14:43:38 31-5-2021