C++ | Digital Clock with RTC

#include <Arduino.h>
#include <TimeLib.h>
#include <Wire.h>
#include <DS1307RTC.h>  // a basic DS1307 library that returns time as a time_t
#include <LiquidCrystal.h>
void digitalClockDisplay();
void printDigits(int digits);
LiquidCrystal lcd(12, 11, 5, 4, 3, 2);

// -------------------------------------------
// Digital Clock with RTC
// www.ardukode.blogspot.com
// -------------------------------------------

void setup()  {
  lcd.begin(16,2);
  while (!Serial);
  delay(200);
}

void loop() {
  tmElements_t tm;
  if (RTC.read(tm))
  {
    lcd.clear();
    lcd.setCursor(0,0);
    lcd.println("Tgl:");
    printDigits(tm.Day);
    lcd.print(".");
    printDigits(tm.Month);
    lcd.print(".");
    lcd.print(tmYearToCalendar(tm.Year));

    lcd.setCursor(0,1);
    lcd.print("Jam: ");
    printDigits(tm.Hour);
    lcd.print(":");
    printDigits(tm.Minute);
    lcd.print(":");
    printDigits(tm.Second);
  }
  else
  {
    if (RTC.chipPresent())
    {
      lcd.print("DS1307 Stop");
    }else
    {
      lcd.print("DS1307 Error");
    }
    delay(9000);
  }
  delay(1000);
}

void printDigits(int digits){
  // utility function for digital clock display: prints preceding colon and leading 0
  if (digits >= 0 && digits < 10)
  {
    lcd.write('0');
  }
  lcd.print(digits);
}