DS3231 Real Time Clock Module I2C

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

RTC_DS3231 rtc;

void setup() {
  Serial.begin(9600);
  while (!Serial) {
    ;
  }

  Wire.begin();

  if (!rtc.begin()) {
    Serial.println("Couldn't find DS3231 RTC module");
    while (1) {
      delay(10);
    }
  }

  // If the RTC lost power, set it to the compile time.
  if (rtc.lostPower()) {
    Serial.println("RTC lost power, setting the time to compile time.");
    rtc.adjust(DateTime(F(__DATE__), F(__TIME__)));
  }

  Serial.println("DS3231 RTC example started.");
}

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

  Serial.print("Date: ");
  Serial.print(now.year());
  Serial.print('-');
  if (now.month() < 10) Serial.print('0');
  Serial.print(now.month());
  Serial.print('-');
  if (now.day() < 10) Serial.print('0');
  Serial.print(now.day());

  Serial.print("  Time: ");
  if (now.hour() < 10) Serial.print('0');
  Serial.print(now.hour());
  Serial.print(':');
  if (now.minute() < 10) Serial.print('0');
  Serial.print(now.minute());
  Serial.print(':');
  if (now.second() < 10) Serial.print('0');
  Serial.println(now.second());

  delay(1000);
}