#include <Wire.h>
#include <RTClib.h>
#include <U8g2lib.h>

RTC_DS1307 rtc;

// U8g2 Constructor for your display, please update the parameters accordingly
U8G2_SSD1306_128X64_NONAME_1_HW_I2C u8g2(U8G2_R0, /* reset=*/ U8X8_PIN_NONE);

void setup() {
  Serial.begin(9600);

  if (!rtc.begin()) {
    Serial.println("Couldn't find RTC");
    while (1);
  }

  if (!rtc.isrunning()) {
    Serial.println("RTC is not running, let's set the time!");
    rtc.adjust(DateTime(F(__DATE__), F(__TIME__)));
  }

  u8g2.begin();
}

void loop() {
  DateTime now = rtc.now();

  u8g2.firstPage();
  do {
    u8g2.setFont(u8g2_font_ncenB08_tr);
    u8g2.setCursor(0, 10);
    u8g2.print(now.day(), DEC);
    u8g2.print('/');
    u8g2.print(now.month(), DEC);
    u8g2.print('/');
    u8g2.print(now.year(), DEC);

    u8g2.setCursor(0,30);
    u8g2.print(now.hour(), DEC);
    u8g2.print(':');
    u8g2.print(now.minute(), DEC);
    u8g2.print(':');
    u8g2.print(now.second(), DEC);
  } while (u8g2.nextPage());

  delay(1000); // doesn't have to be 1000
}