Arduino Mega2560 | Library: https://github.com/rodan/ds3231 | Pins: SDA to Pin20 | SCL to Pin21 | VCC to 5v | GND to GND |

Clock.pde

// include the library code:
#include <LiquidCrystal.h>

#include <Wire.h>

#include "ds3231.h"

// initialize the library with the numbers of the interface pins
LiquidCrystal lcd(12, 11, 5, 4, 3, 2);
int sensorValue;

byte full[8] = {
  B11111,
  B11111,
  B11111,
  B11111,
  B11111,
  B11111,
  B11111,
};

byte empty[8] = {
  B00000,
  B00000,
  B00000,
  B00000,
  B00000,
  B00000,
  B00000,
};

void setup() {
  lcd.createChar(0, empty);
  lcd.createChar(1, full);
  lcd.begin(16, 2);
  pinMode(A0, INPUT);
  digitalWrite(A0, HIGH);
  Serial.begin(19200);
  Wire.begin();
  DS3231_init(0x06);
}

void loop() {
  struct ts now;
  DS3231_get(&now);
  char time[5];
  sprintf(time,"%02d:%02d", now.hour, now.min);
  lcd.setCursor(0, 0);
  lcd.print(time);
  sensorValue = analogRead(A0) / 64;
  for(int i = 0; i < 16; i++) {
    lcd.setCursor(i, 1);
    if(i <= sensorValue + 1) lcd.write(byte(1));
    else lcd.write(byte(0));
  }
  delay(80);
}