RTC with ATmega32 and DS1307 showing the year completely wrong

Question

I'm building a clock/calendar with an ATmega, a DS1307, and a 20*4 LCD (LM044L).

I have implemented the code showing the time correctly, I have initialized the RTC too, but for some reason when I try to print the date, the year is scrambled up into some nonsense number, although the day and month are shown correctly.

I have written 2 functions to give date and time a default value for the time being. I will put the parts of the code that I wrote, and also the circuit I have built in Proteus. Ignore the buttons and the keypad as I have not yet implemented any code for them.

PS. Please help me understand why this happened, I am not looking for suggestion to use other pieces of hardware, or changing the code to a whole other method of implementation, I'm trying to get what is going on with my code.

char year=0, month=0, day=0, dow=0; // dow=day of week
char date[];
char time[]={0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}, hour=0, min=0, sec=0;
void reset_clock(void);
void time_defaultinit();
void date_defaultinit();

---

void time_defaultinit()
{
    hour=15;
    min=18;
    sec=55;
    rtc_set_time(hour, min, sec);
}

void date_defaultinit()
{
    rtc_set_date(3, 17, 05, 2002);
}

---

The part below is what is included in the main function:

time_defaultinit();
date_defaultinit();

while (1) {
    if (!resetclock) {
        reset_clock();
    }
    lcd_clear();
    rtc_get_date(&dow, &day, &month, &year);
    sprintf(date, "%d %04d/%02d/%02d", dow, year, month, day);
    lcd_gotoxy(0, 0);
    lcd_puts(date);
    rtc_get_time(&hour, &min, &sec);
    sprintf(time, "%02d:%02d:%02d", hour, min, sec);
    lcd_gotoxy(5, 2);
    lcd_puts(time);
    delay_ms(850); 
}

EDIT: The results were the same back when I used char variables for the manual initialization of the rtc_set_date function as below:

void date_defaultinit()
{
    year=2002; //char year
    month=5; //char month
    day=17; //char day
    dow=3; //char dow
    rtc_set_date(dow, day, month, year);
}

Answer 1

You should have said in the first post that you use a paid compiler and libraries that come with it.

The problem is solved by downloading and reading the compiler manual.

The manual documents that the date setting and getting functions consider year as char, so you can't initialize it to 2002 and it won't read back as 2002.

The manual also happens to provide an example project that initializes time and date and prints it on LCD, from where it is also obvious how to use the years.

The wrong usage of the functions should have caused compiler warnings so either you don't have the relevant compiler warnings enabled or chose to ignore them. You might want to let the compiler warn you when it sees that something is not right and fix the warnings.