Getting Time From Internet Using ESP8266 – NTP

timeClient.setTimeOffset(19800); //IST is UTC+5:30 Hrs

The Code

#include <ESP8266WiFi.h>
#include <NTPClient.h>
#include <WiFiUdp.h>

// Replace with your network credentials
const char *ssid     = "XXXXX";
const char *password = "XXXXXXXXXXXXXXX";

// Define NTP Client to get time
WiFiUDP ntpUDP;
NTPClient timeClient(ntpUDP, "pool.ntp.org");

//Week Days
String weekDays[7]={"Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"};

//Month names
String months[12]={"January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"};

void setup() {
  // Initialize Serial Monitor
  Serial.begin(115200);
  
  // Connect to Wi-Fi
  Serial.print("Connecting to ");
  Serial.println(ssid);
  WiFi.begin(ssid, password);
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }

// 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);  //IST is UTC+5:30 Hrs
}

void loop() {
  timeClient.update();

  unsigned long epochTime = timeClient.getEpochTime();
  Serial.print("Epoch Time: ");
  Serial.println(epochTime);
  
  String formattedTime = timeClient.getFormattedTime();
  Serial.print("Formatted Time: ");
  Serial.println(formattedTime);  

  int currentHour = timeClient.getHours();
  Serial.print("Hour: ");
  Serial.println(currentHour);  

  int currentMinute = timeClient.getMinutes();
  Serial.print("Minutes: ");
  Serial.println(currentMinute); 
   
  int currentSecond = timeClient.getSeconds();
  Serial.print("Seconds: ");
  Serial.println(currentSecond);  

  String weekDay = weekDays[timeClient.getDay()];
  Serial.print("Week Day: ");
  Serial.println(weekDay);    

  //Get a time structure
  struct tm *ptm = gmtime ((time_t *)&epochTime); 

  int monthDay = ptm->tm_mday;
  Serial.print("Month day: ");
  Serial.println(monthDay);

  int currentMonth = ptm->tm_mon+1;
  Serial.print("Month: ");
  Serial.println(currentMonth);

  String currentMonthName = months[currentMonth-1];
  Serial.print("Month name: ");
  Serial.println(currentMonthName);

  int currentYear = ptm->tm_year+1900;
  Serial.print("Year: ");
  Serial.println(currentYear);

  //Print complete date:
  String currentDate = String(currentYear) + "-" + String(currentMonth) + "-" + String(monthDay);
  Serial.print("Current date: ");
  Serial.println(currentDate);

  Serial.println("");

  delay(2000);
}

Code Working

Include the necessary Libraries.

#include <ESP8266WiFi.h> 
#include <NTPClient.h> 
#include <WiFiUdp.h>

Insert Network Credentials

• Insert your network credentials in the following variables so that the ESP8266 can connect to your router to have access to the internet to request date and time from the NTP server.

const char *ssid = "XXXXX";
const char *password = "XXXXXXXXXXXXXXX";

Define an NTP client to get date and time from Internet

We’ll request the time from pool.ntp.org, which is a cluster of times servers that anyone can use to request the time. The pool.ntp.org automatically picks time servers which are geographically close for you. But if you want to choose explicitly, use one of the sub-zones of pool.ntp.org.

WiFiUDP ntpUDP;
NTPClient timeClient(ntpUDP, "pool.ntp.org");

Arrays to hold the Day and Month Names

Next, we create two arrays to hold the days of the week and the month names.

//Week Days
String weekDays[7]={"Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"}; 
//Month names 
String months[12]={"January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"};

setup()

The setup() function in Arduino is used to write the part of code which we want to run only once at the beginning. In this function, we usually do the initializations.

Initialize Serial Monitor

In the setup(), initialize the Serial Monitor to display the information.

Serial.begin(115200);

Connect the ESP8266 to the internet.

// Connect to Wi-Fi 
Serial.print("Connecting to "); 
Serial.println(ssid); 
WiFi.begin(ssid, password); 
while (WiFi.status() != WL_CONNECTED) { 
   delay(500); 
   Serial.print("."); 
}

Initialize the NTPClient

The begin() function is used to initialize the timeClient.

timeClient.begin();

Set Timezone

You can use the setTimeOffset() method to adjust the time for your timezone in seconds.

timeClient.setTimeOffset(19800);

Here are some examples for different time zones:

• GMT +1 = 3600
• GMT +8 = 28800
• GMT -1 = -3600
• GMT 0 = 0

In India, the offset is UTC+5.30. Therefore the offset in terms of seconds is (5*60 +30)*60 seconds = 19800 seconds

In the loop(), call the update() function to get the current date and time from the NTP server.

timeClient.update();

Get Time

Then, we can use the functions provided by the library to get time.

• To get the epoch time:

unsigned long epochTime = timeClient.getEpochTime(); 
Serial.print("Epoch Time: "); 
Serial.println(epochTime);

• The getFormattedTime()function returns the time in HH:MM:SS format.

String formattedTime = timeClient.getFormattedTime(); 
Serial.print("Formatted Time: "); 
Serial.println(formattedTime);

You can get the hours, minutes or seconds separately using the getHours(), getMinutes() and getSeconds()functions as follows:

int currentHour = timeClient.getHours(); 
Serial.print("Hour: "); 
Serial.println(currentHour); 

int currentMinute = timeClient.getMinutes(); 
Serial.print("Minutes: "); 
Serial.println(currentMinute); 

int currentSecond = timeClient.getSeconds(); 
Serial.print("Seconds: "); 
Serial.println(currentSecond);

Get Date

• The getDay() function returns a number from 0 to 6, in which 0 corresponds to Sunday and 6 to Saturday. So, we can access the week day name from the array we’ve created previously as follows

String weekDay = weekDays[timeClient.getDay()]; 
Serial.print("Week Day: "); 
Serial.println(weekDay);

• The NTP Client doesn’t come with functions to get the date. So, we need to create a time structure (struct tm) and then, access its elements to get information about the date.

struct tm *ptm = gmtime ((time_t *)&epochTime);

The time structure contains the following elements:

• • tm_sec: seconds after the minute;
  • tm_min: minutes after the hour;
  • tm_hour: hours since midnight;
  • tm_mday: day of the month;
  • tm_year: years since 1900;
  • tm_wday: days since Sunday;
  • tm_yday: days since January 1;
  • tm_isdst: Daylight Saving Time flag;
  • tm structure documentation.

• The following lines get the day of the month as follows:

int monthDay = ptm->tm_mday; 
Serial.print("Month day: "); 
Serial.println(monthDay);

• To get the other elements, you use a similar approach. For example, for the month:

int currentMonth = ptm->tm_mon+1; 
Serial.print("Month: "); 
Serial.println(currentMonth);

Because the tm_mdaystarts at 0, we add 1 to the month so that January corresponds to 1, February to 2, and so on.

• Then, we can get the name of the month using the months array we’ve created previously. The arrays numbering starts at 0, that’s why we subtract 1.

String currentMonthName = months[currentMonth-1]; 
Serial.print("Month name: "); 
Serial.println(currentMonthName);

• To get the year, we need to add 1900 because the tm_yearsaves the number of years after 1900.

int currentYear = ptm->tm_year+1900; 
Serial.print("Year: "); 
Serial.println(currentYear);

• Finally, we create a String called currentDate that holds the current date in the YYYY-MM-DD format.

String currentDate = String(currentYear) + "-" + String(currentMonth) + "-" + String(monthDay); 
Serial.print("Current date: "); 
Serial.println(currentDate);