#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
#include <WiFi.h>
#include <WiFiUdp.h>
#include <NTPClient.h>          
#include <TimeLib.h>           

#define SCREEN_WIDTH 128 // OLED display width,  in pixels
#define SCREEN_HEIGHT 64 // OLED display height, in pixels
Adafruit_SSD1306 lcd(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, -1);

const char *ssid     = "ZTE_2.4G_fCeGuw";    /*Replace with your network SSID*/
const char *password = "w3mnw4eu";  /*Replace with network password*/
WiFiUDP ntpUDP;
NTPClient timeClient(ntpUDP, "time.nist.gov", 18000, 60000);

char Time[ ] = "TIME:00:00:00";
char Date[ ] = "DATE:00/00/2000";
byte last_second, second_, minute_, hour_, day_, month_;
int year_;

void setup(){
  Serial.begin(115200);
  // initialize OLED display with address 0x3C for 128x64
  if (!oled.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {
    Serial.println(F("SSD1306 allocation failed"));
    while (true);
  }
  lcd.setCursor(0, 0);  /*Set cursor*/
  lcd.print("Time");  /*print time on LCD*/
  lcd.setCursor(0, 1);  /*Set LCD cursor*/
  lcd.print(Date);  /*Print date*/

  WiFi.begin(ssid, password);  /*begin WiFi*/
  Serial.print("Connecting.");
  while ( WiFi.status() != WL_CONNECTED ) {
    delay(500);
    Serial.print(".");
  }
  Serial.println("connected");
  timeClient.begin();
  delay(1000);
  lcd.clear();  /*clear LCD display*/
}

void loop(){
  timeClient.update();
  unsigned long unix_epoch = timeClient.getEpochTime();    // Get Unix epoch time from the NTP server
  second_ = second(unix_epoch);
  if (last_second != second_) {
    minute_ = minute(unix_epoch);
    hour_   = hour(unix_epoch);
    day_    = day(unix_epoch);
    month_  = month(unix_epoch);
    year_   = year(unix_epoch);
    Time[12] = second_ % 10 + 48;
    Time[11] = second_ / 10 + 48;
    Time[9]  = minute_ % 10 + 48;
    Time[8]  = minute_ / 10 + 48;
    Time[6]  = hour_   % 10 + 48;
    Time[5]  = hour_   / 10 + 48;
    Date[5]  = day_   / 10 + 48;
    Date[6]  = day_   % 10 + 48;
    Date[8]  = month_  / 10 + 48;
    Date[9]  = month_  % 10 + 48;
    Date[13] = (year_   / 10) % 10 + 48;
    Date[14] = year_   % 10 % 10 + 48;
    Serial.println(Time);  /*Prints time on serial monitor*/
    Serial.println(Date);  /*Print date on serial monitor*/
    lcd.setCursor(0, 0);  /*Set LCD cursor*/
    lcd.print(Time);  /*display time on LCD*/
    lcd.setCursor(0, 1); /*Set LCD cursor*/
    lcd.print(Date);  /*Display date on LCD*/
    last_second = second_;
  }
  delay(200);
}