// Date and time functions using a DS1307 RTC connected via I2C and Wire lib
#include "RTClib.h"
RTC_DS1307 rtc;
char time_buf[16];

void setup () {
  Serial.begin(57600);

#ifndef ESP8266
  while (!Serial); // wait for serial port to connect. Needed for native USB
#endif

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

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

void loop () {
  DateTime now = rtc.now();
  sprintf(time_buf, "%04u/%02u/%02u %02u:%02u:%02u", now.year(), now.month(), now.day(), now.hour(), now.minute(), now.second());
  Serial.print(time_buf);
  Serial.println();
  delay(3000);
}