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

RTC_DS1307 rtc;


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();
    while (1) delay(10);
  }

  if (! rtc.isrunning()) {
    Serial.println("RTC is NOT running, let's set the time!");
    // When time needs to be set on a new device, or after a power loss, the
    // following line sets the RTC to the date & time this sketch was compiled
    rtc.adjust(DateTime(F(__DATE__), F(__TIME__)));
    // This line sets the RTC with an explicit date & time, for example to set
    // January 21, 2014 at 3am you would call:
    // rtc.adjust(DateTime(2014, 1, 21, 3, 0, 0));
  }

  // When time needs to be re-set on a previously configured device, the
  // following line sets the RTC to the date & time this sketch was compiled
  // rtc.adjust(DateTime(F(__DATE__), F(__TIME__)));
  // This line sets the RTC with an explicit date & time, for example to set
  // January 21, 2014 at 3am you would call:
  // rtc.adjust(DateTime(2014, 1, 21, 3, 0, 0));
}

void loop() {

   DateTime now = rtc.now();

  //buffer can be defined using following combinations:
  //hh - the hour with a leading zero (00 to 23)
  //mm - the minute with a leading zero (00 to 59)
  //ss - the whole second with a leading zero where applicable (00 to 59)
  //YYYY - the year as four digit number
  //YY - the year as two digit number (00-99)
  //MM - the month as number with a leading zero (01-12)
  //MMM - the abbreviated English month name ('Jan' to 'Dec')
  //DD - the day as number with a leading zero (01 to 31)
  //DDD - the abbreviated English day name ('Mon' to 'Sun')

   char buf1[] = "hh:mm";
   Serial.println(now.toString(buf1));

   char buf2[] = "YYMMDD-hh:mm:ss";
   Serial.println(now.toString(buf2));

   char buf3[] = "Today is DDD, MMM DD YYYY";
   Serial.println(now.toString(buf3));

   char buf4[] = "MM-DD-YYYY";
   Serial.println(now.toString(buf4));

   delay(1000);
}