NTP server

first, get NTP client library for ESP32, and save in Arduino library folder 

https://randomnerdtutorials.com/esp32-ntp-client-date-time-arduino-ide/

Then set time, GMT +5.5 to view Sri Lanka time 

Then upload the code and view serial monitor using Arduino IDE, that should indicate as follows 

///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

#include <WiFi.h>

#include <NTPClient.h>

#include <WiFiUdp.h>

// Replace with your network credentials

const char* ssid     = "Your SSD"; // 

const char* password = "Your Password";

// Define NTP Client to get time

WiFiUDP ntpUDP;

NTPClient timeClient(ntpUDP);

// Variables to save date and time

String formattedDate;

String dayStamp;

String timeStamp;

void setup() {

  // Initialize Serial Monitor

  Serial.begin(115200);

  Serial.print("Connecting to ");

  Serial.println(ssid);

  WiFi.begin(ssid, password);

  while (WiFi.status() != WL_CONNECTED) {

    delay(500);

    Serial.print(".");

  }

  // Print local IP address and start web server

  Serial.println("");

  Serial.println("WiFi connected.");

  Serial.println("IP address: ");

  Serial.println(WiFi.localIP());

// Initialize a NTPClient to get time

  timeClient.begin();

  // Set offset time in seconds to adjust for your timezone, for example:

  // GMT +1 = 3600

  // GMT +8 = 28800

  // GMT -1 = -3600

  // GMT 0 = 0

  timeClient.setTimeOffset(19800);

}

void loop() {

  while(!timeClient.update()) {

    timeClient.forceUpdate();

  }

  // The formattedDate comes with the following format:

  // 2018-05-28T16:00:13Z

  // We need to extract date and time

  formattedDate = timeClient.getFormattedDate();

  Serial.println(formattedDate);

  // Extract date

  int splitT = formattedDate.indexOf("T");

  dayStamp = formattedDate.substring(0, splitT);

  Serial.print("DATE: ");

  Serial.println(dayStamp);

  // Extract time

  timeStamp = formattedDate.substring(splitT+1, formattedDate.length()-1);

  Serial.print("HOUR: ");

  Serial.println(timeStamp);

  delay(1000);

}

/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

Unix Time 

/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

#include <TimeLib.h>

unsigned long offset_days = 3;    // 3 days
unsigned long t_unix_date1, t_unix_date2;

void setup() {
  Serial.begin(115200);
  t_unix_date1 = 1564398600;
  Serial.print("t_unix_date1: ");
  Serial.println(t_unix_date1);
  offset_days = offset_days * 86400;    // convert number of days to seconds
  t_unix_date2 = 1564398600 + offset_days;
  Serial.print("t_unix_date2: ");
  Serial.println(t_unix_date2);
  printf("Date1: %4d-%02d-%02d %02d:%02d:%02d\n", year(t_unix_date1), month(t_unix_date1), day(t_unix_date1), hour(t_unix_date1), minute(t_unix_date1), second(t_unix_date1));
  printf("Date2: %4d-%02d-%02d %02d:%02d:%02d\n", year(t_unix_date2), month(t_unix_date2), day(t_unix_date2), hour(t_unix_date2), minute(t_unix_date2), second(t_unix_date2));
}

void loop() {



}

OLED interface with ESP8266

This code used to interface with OLED, 

bit map code was generated using http://javl.github.io/image2cpp/ 

//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

 #include <SPI.h>

#include <Wire.h>

#include <Adafruit_GFX.h>

#include <Adafruit_SSD1306.h>

#define SCREEN_WIDTH 128 // OLED display width, in pixels

#define SCREEN_HEIGHT 64 // OLED display height, in pixels

// Declaration for SSD1306 display connected using software SPI (default case):

#define     OLED_MOSI        D7

#define     OLED_CLK          D5

#define     OLED_DC             D2

#define     OLED_CS             D8

#define     OLED_RESET      D3

Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT,

  OLED_MOSI, OLED_CLK, OLED_DC, OLED_RESET, OLED_CS);

const unsigned char myBitmap [] PROGMEM = {

0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 

0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 

0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 

0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 

0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 

0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xfe, 0x00, 0x3f, 0xff, 0xff, 0xff, 0xff, 0xff, 

0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x00, 0x00, 0x01, 0xff, 0xff, 0xff, 0xff, 0xff, 

0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xe0, 0x00, 0x00, 0x00, 0x1f, 0xff, 0xff, 0xff, 0xff, 

0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xfe, 0x00, 0x00, 0x00, 0x00, 0x07, 0xff, 0xff, 0xff, 0xff, 

0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xf0, 0x00, 0x00, 0x00, 0x00, 0x01, 0xff, 0xff, 0xff, 0xff, 

0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xe0, 0x00, 0x00, 0x00, 0x00, 0x00, 0x7f, 0xff, 0xff, 0xff, 

0xff, 0xff, 0xff, 0xff, 0xff, 0xfc, 0xc0, 0x00, 0x00, 0x00, 0x00, 0x00, 0x3f, 0xff, 0xff, 0xff, 

0xff, 0xff, 0xff, 0xff, 0xff, 0xf1, 0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x1f, 0xff, 0xff, 0xff, 

0xff, 0xff, 0xff, 0xff, 0xff, 0x81, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x0f, 0xff, 0xff, 0xff, 

0xff, 0xff, 0xff, 0xff, 0xfe, 0x00, 0x00, 0x00, 0x00, 0x00, 0x10, 0x00, 0x07, 0xff, 0xff, 0xff, 

0xff, 0xff, 0xff, 0xff, 0xf8, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02, 0x00, 0x07, 0xff, 0xff, 0xff, 

0xff, 0xff, 0xff, 0xff, 0xe0, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x80, 0x03, 0xff, 0xff, 0xff, 

0xff, 0xff, 0xff, 0xff, 0x80, 0x07, 0x80, 0x00, 0x00, 0x00, 0x00, 0x60, 0x03, 0xff, 0xff, 0xff, 

0xff, 0xff, 0xff, 0xfe, 0x00, 0x1f, 0x80, 0x00, 0x00, 0x00, 0x00, 0x30, 0x03, 0xff, 0xff, 0xff, 

0xff, 0xff, 0xff, 0xf8, 0x00, 0x3f, 0x80, 0x00, 0x00, 0x00, 0x00, 0x0c, 0x01, 0xff, 0xff, 0xff, 

0xff, 0xff, 0xff, 0xf0, 0x00, 0x3f, 0x80, 0x00, 0x00, 0x00, 0x00, 0x06, 0x01, 0xff, 0xff, 0xff, 

0xff, 0xff, 0xff, 0xc0, 0x00, 0x1f, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x81, 0xff, 0xff, 0xff, 

0xff, 0xff, 0xff, 0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xc1, 0xff, 0xff, 0xff, 

0xff, 0xff, 0xff, 0x00, 0x00, 0x01, 0x80, 0xc0, 0x0e, 0x00, 0x0e, 0x00, 0x61, 0xff, 0xff, 0xff, 

0xff, 0xff, 0xfe, 0x00, 0x00, 0x7f, 0x87, 0xf8, 0x7f, 0xc0, 0xff, 0xf8, 0x71, 0xff, 0xff, 0xff, 

0xff, 0xff, 0xfc, 0x00, 0x00, 0x7f, 0x9f, 0xfc, 0xff, 0xe3, 0xf0, 0xf8, 0x31, 0xff, 0xff, 0xff, 

0xff, 0xff, 0xf8, 0x00, 0x00, 0x1f, 0x90, 0xff, 0x07, 0xf3, 0xe0, 0x70, 0x19, 0xff, 0xff, 0xff, 

0xff, 0xff, 0xf8, 0x00, 0x00, 0x1f, 0x80, 0x7e, 0x03, 0xf3, 0xf0, 0x20, 0x19, 0xff, 0xff, 0xff, 

0xff, 0xff, 0xfc, 0x00, 0x00, 0x1f, 0x80, 0x7e, 0x03, 0xf3, 0xf8, 0x00, 0x1d, 0xff, 0xff, 0xff, 

0xff, 0xff, 0xfc, 0x00, 0x00, 0x1f, 0x80, 0x7e, 0x03, 0xf1, 0xff, 0x80, 0x1f, 0xff, 0xff, 0xff, 

0xff, 0xff, 0xfe, 0x00, 0x00, 0x1f, 0x80, 0x7e, 0x03, 0xf0, 0xff, 0xe0, 0x1f, 0xff, 0xff, 0xff, 

0xff, 0xff, 0xff, 0x80, 0x00, 0x1f, 0x80, 0x7e, 0x03, 0xf0, 0x1f, 0xf8, 0x1f, 0xff, 0xff, 0xff, 

0xff, 0xff, 0xff, 0xc0, 0x00, 0x1f, 0x80, 0x7e, 0x03, 0xf0, 0x03, 0xf8, 0x1f, 0xff, 0xff, 0xff, 

0xff, 0xff, 0xff, 0xf0, 0x00, 0x1f, 0x80, 0x7e, 0x03, 0xf0, 0x00, 0xfc, 0x3f, 0xff, 0xff, 0xff, 

0xff, 0xff, 0xff, 0xfc, 0x00, 0x1f, 0x80, 0x7e, 0x03, 0xf0, 0x00, 0xf8, 0x3f, 0xff, 0xff, 0xff, 

0xff, 0xff, 0xff, 0xff, 0x00, 0x1f, 0xc0, 0xff, 0x03, 0xf8, 0x01, 0xf8, 0x7f, 0xff, 0xff, 0xff, 

0xff, 0xff, 0xff, 0xff, 0xc0, 0x7f, 0xf1, 0xff, 0x8f, 0xfe, 0x03, 0xe0, 0xef, 0xff, 0xff, 0xff, 

0xff, 0xff, 0xff, 0xff, 0xf0, 0x00, 0x00, 0x30, 0x00, 0x00, 0x0e, 0x03, 0x9f, 0xff, 0xff, 0xff, 

0xff, 0xff, 0xff, 0xff, 0xfc, 0x00, 0x00, 0x18, 0x00, 0x00, 0x00, 0x0f, 0x1f, 0xff, 0xff, 0xff, 

0xff, 0xff, 0xff, 0xff, 0xff, 0x00, 0x00, 0x06, 0x00, 0x00, 0x00, 0x3c, 0x3f, 0xff, 0xff, 0xff, 

0xff, 0xff, 0xff, 0xff, 0xff, 0x80, 0x00, 0x03, 0x00, 0x00, 0x00, 0xf0, 0x3f, 0xff, 0xff, 0xff, 

0xff, 0xff, 0xff, 0xff, 0xff, 0xe0, 0x00, 0x00, 0xc0, 0x00, 0x0f, 0x00, 0x7f, 0xff, 0xff, 0xff, 

0xff, 0xff, 0xff, 0xff, 0xff, 0xf0, 0x00, 0x00, 0x70, 0x00, 0x7c, 0x00, 0x7f, 0xff, 0xff, 0xff, 

0xff, 0xff, 0xff, 0xff, 0xff, 0xfc, 0x00, 0x00, 0x1c, 0x0f, 0x80, 0x00, 0xff, 0xff, 0xff, 0xff, 

0xff, 0xff, 0xff, 0xff, 0xff, 0xfe, 0x00, 0x00, 0x07, 0xf0, 0x00, 0x01, 0xff, 0xff, 0xff, 0xff, 

0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x00, 0x0f, 0xc1, 0xc0, 0x00, 0x03, 0xff, 0xff, 0xff, 0xff, 

0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xc0, 0x00, 0x00, 0xf0, 0x00, 0x07, 0xff, 0xff, 0xff, 0xff, 

0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xc0, 0x00, 0x00, 0x1e, 0x00, 0x0f, 0xff, 0xff, 0xff, 0xff, 

0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xe0, 0x00, 0x00, 0x07, 0x80, 0x0f, 0xff, 0xff, 0xff, 0xff, 

0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xf0, 0x00, 0x00, 0x01, 0xf0, 0x3f, 0xff, 0xff, 0xff, 0xff, 

0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xf0, 0x00, 0x00, 0x00, 0x7e, 0x7f, 0xff, 0xff, 0xff, 0xff, 

0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xf8, 0x00, 0x00, 0x00, 0x0f, 0xff, 0xff, 0xff, 0xff, 0xff, 

0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xfc, 0x00, 0x00, 0x00, 0x03, 0xff, 0xff, 0xff, 0xff, 0xff, 

0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xfe, 0x00, 0x00, 0x00, 0x07, 0xff, 0xff, 0xff, 0xff, 0xff, 

0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x00, 0x00, 0x00, 0x0f, 0xff, 0xff, 0xff, 0xff, 0xff, 

0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x80, 0x00, 0x00, 0x3f, 0xff, 0xff, 0xff, 0xff, 0xff, 

0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xc0, 0x00, 0x00, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 

0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xf0, 0x00, 0x07, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 

0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xfe, 0x00, 0x3f, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 

0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 

0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 

0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 

0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 

0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff

};

void setup() {

  Serial.begin(9600);

  // SSD1306_SWITCHCAPVCC = generate display voltage from 3.3V internally

  if(!display.begin(SSD1306_SWITCHCAPVCC)) {

    Serial.println(F("SSD1306 allocation failed"));

    for(;;); // Don't proceed, loop forever

  }

  // Show initial display buffer contents on the screen --

  // the library initializes this with an Adafruit splash screen.

  //display.display();

  //delay(2000); // Pause for 2 seconds

  // Clear the buffer

  display.clearDisplay();

  testscrolltext();

  // Clear the buffer.

  display.clearDisplay();

  // Display bitmap

  display.drawBitmap(0, 0,  myBitmap, 128, 64, BLACK, WHITE);

  display.display();

}

void loop() {

}

void testscrolltext(void) {

  display.clearDisplay();

  display.setTextSize(2); // Draw 2X-scale text

  display.setTextColor(WHITE);

  display.setCursor(0, 0);

  display.println(F("Asanka"));

  display.println(F("Lakmal"));

  display.println(F("Morawaka"));

  display.display();      // Show initial text

  delay(100);

  // Scroll in various directions, pausing in-between:

  display.startscrollright(0x00, 0x0F);

  delay(2000);

  display.stopscroll();

  delay(1000);

  display.startscrollleft(0x00, 0x0F);

  delay(2000);

  display.stopscroll();

  delay(1000);

  display.startscrolldiagright(0x00, 0x07);

  delay(2000);

  display.startscrolldiagleft(0x00, 0x07);

  delay(2000);

  display.stopscroll();

  delay(1000);

}