#include <RTClib.h>
RTC_DS1307 rtc;

char daysOfTheWeek[7][12] = {
  "SUN", "MON", "TUe", "WED", "THU", "FRI", "SAT"
};

int oldSecond; // print new data every change in "second"

void setup () {
  Serial.begin(115200);
  rtc.begin();

  // if (! rtc.begin()) { // uncomment this block if you can not get an RTC reading
  //   Serial.println("Couldn't find RTC");
  //   Serial.flush();
  //   while (1);
  // }

  // automatically set the RTC to the date & time on PC this sketch was compiled
  // rtc.adjust(DateTime(F(__DATE__), F(__TIME__)));

  // manually set RTC with an explicit date & time...
  // January 21, 2021 at 3am you would call:
  // rtc.adjust(DateTime(2021, 1, 21, 3, 0, 0));
}

void loop () {
  DateTime now = rtc.now();
  if (oldSecond != now.second()) { // only print when seconds change
    zeropad(now.year(), "/"); // format the value and add a delimeter
    zeropad(now.month(), "/");
    zeropad(now.day(), " (");
    Serial.print(daysOfTheWeek[now.dayOfTheWeek()]);
    Serial.print(") ");
    zeropad(now.hour(), ":");
    zeropad(now.minute(), ":");
    zeropad(now.second(), " ");

    oldSecond = now.second(); // store old "seconds"
    Serial.println();
  }
}

void zeropad(int value, char symbol[]) {
  if (value < 10)
    Serial.print("0"); // pad the units value
  Serial.print(value); // print the value (year, month, day, hour, minute, second)
  Serial.print(symbol); // print a delimiter symbol
}