In this tutorial, you’ll learn how to properly get the time with the ESP32 for your timezone and consider daylight saving time (if that’s the case). The ESP32 will request the time from an NTP server, and the time will be automatically adjusted for your timezone with or without daylight saving time.
Quick Answer: call setenv(“TZ”, timezone, 1), where timezone is one of the timezones listed here. Then, call tzset() to update to that timezone.
If you’re getting started, we recommend taking a look at the following tutorial first to learn how to get date and time from an NTP server:
- ESP32 NTP Client-Server: Get Date and Time (Arduino IDE)
In that previous tutorial, we’ve shown an option to set up your timezone. However, that example doesn’t take into account daylight saving time. Continue reading this tutorial to learn how to set up the timezone and daylight saving time properly.
Thanks to one of our readers (Hardy Maxa) who shared this information with us.
ESP32 Setting Timezone with Daylight Saving Time
According to documentation:
“To set local timezone, use setenv and tzset POSIX functions. First, call setenv to set TZ environment variable to the correct value depending on device location. Format of the time string is described in libc documentation. Next, call tzset to update C library runtime data for the new time zone. Once these steps are done, localtime function will return correct local time, taking time zone offset and daylight saving time into account.”
You can check a list of timezone string variables here.
For example, I live in Porto. The timezone is Europe/Lisbon. From the list of timezone string variables, I see that the timezone string variable for my location is WET0WEST,M3.5.0/1,M10.5.0, so after connecting to the NTP server, to get the time for my location I need to call:
setenv("TZ","WET0WEST,M3.5.0/1,M10.5.0",1);Followed by:
tzset();Let’s look at a demo sketch to understand how it works and how to use it in your ESP32 project.
ESP32 Timezone and DST Example Sketch
The following example was provided by one of our followers (Hardy Maxa), we’ve just made a few modifications.
Copy the following code to your Arduino IDE.
// RTC demo for ESP32, that includes TZ and DST adjustments// Get the POSIX style TZ format string from https://github.com/nayarsystems/posix_tz_db/blob/master/zones.csv// Created by Hardy Maxa// Complete project details at: https://RandomNerdTutorials.com/esp32-ntp-timezones-daylight-saving/#include <WiFi.h>#include "time.h"const char * ssid="REPLACE_WITH_YOUR_SSID";const char * wifipw="REPLACE_WITH_YOUR_PASSWORD";void setTimezone(String timezone){ Serial.printf(" Setting Timezone to %s\n",timezone.c_str()); setenv("TZ",timezone.c_str(),1); // Now adjust the TZ. Clock settings are adjusted to show the new local time tzset();}void initTime(String timezone){ struct tm timeinfo; Serial.println("Setting up time"); configTime(0, 0, "pool.ntp.org"); // First connect to NTP server, with 0 TZ offset if(!getLocalTime(&timeinfo)){ Serial.println(" Failed to obtain time"); return; } Serial.println(" Got the time from NTP"); // Now we can set the real timezone setTimezone(timezone);}void printLocalTime(){ struct tm timeinfo; if(!getLocalTime(&timeinfo)){ Serial.println("Failed to obtain time 1"); return; } Serial.println(&timeinfo, "%A, %B %d %Y %H:%M:%S zone %Z %z ");}void startWifi(){ WiFi.begin(ssid, wifipw); Serial.println("Connecting Wifi"); while (WiFi.status() != WL_CONNECTED) { Serial.print("."); delay(500); } Serial.print("Wifi RSSI="); Serial.println(WiFi.RSSI());}void setTime(int yr, int month, int mday, int hr, int minute, int sec, int isDst){ struct tm tm; tm.tm_year = yr - 1900; // Set date tm.tm_mon = month-1; tm.tm_mday = mday; tm.tm_hour = hr; // Set time tm.tm_min = minute; tm.tm_sec = sec; tm.tm_isdst = isDst; // 1 or 0 time_t t = mktime(&tm); Serial.printf("Setting time: %s", asctime(&tm)); struct timeval now = { .tv_sec = t }; settimeofday(&now, NULL);}void setup(){ Serial.begin(115200); Serial.setDebugOutput(true); startWifi(); initTime("WET0WEST,M3.5.0/1,M10.5.0"); // Set for Melbourne/AU printLocalTime();}void loop() { int i; // put your main code here, to run repeatedly: Serial.println("Lets show the time for a bit. Starting with TZ set for Melbourne/Australia"); for(i=0; i<10; i++){ delay(1000); printLocalTime(); } Serial.println(); Serial.println("Now - change timezones to Berlin"); setTimezone("CET-1CEST,M3.5.0,M10.5.0/3"); for(i=0; i<10; i++){ delay(1000); printLocalTime(); } Serial.println(); Serial.println("Now - Lets change back to Lisbon and watch Daylight savings take effect"); setTimezone("WET0WEST,M3.5.0/1,M10.5.0"); printLocalTime(); Serial.println(); Serial.println("Now change the time. 1 min before DST takes effect. (1st Sunday of Oct)"); Serial.println("AEST = Australian Eastern Standard Time. = UTC+10"); Serial.println("AEDT = Australian Eastern Daylight Time. = UTC+11"); setTime(2021,10,31,0,59,50,0); // Set it to 1 minute before daylight savings comes in. for(i=0; i<20; i++){ delay(1000); printLocalTime(); } Serial.println("Now change the time. 1 min before DST should finish. (1st Sunday of April)"); setTime(2021,3,28,1,59,50,1); // Set it to 1 minute before daylight savings comes in. Note. isDst=1 to indicate that the time we set is in DST. for(i=0; i<20; i++){ delay(1000); printLocalTime(); } // Now lets watch the time and see how long it takes for NTP to fix the clock Serial.println("Waiting for NTP update (expect in about 1 hour)"); while(1) { delay(1000); printLocalTime(); }}How the Code Works
First, you need to include the WiFi library to connect the ESP32 to the internet (NTP server) and the time library to deal with time.
#include <WiFi.h>#include "time.h"To set the timezone, we created a function called setTimezone() that accepts as an argument a timezone string.
void setTimezone(String timezone){Inside that function, we call the setenv() function for the TZ (timezone) parameter to set the timezone with whatever timezone you pass as an argument to the setTimezone() function.
setenv("TZ",timezone.c_str(),1); // Now adjust the TZ. Clock settings are adjusted to show the new local timeAfter that, call the tzset() function for the changes to take effect.
tzset();We won’t go into detail about the other functions declared in the code because those were already explained in a previous tutorial:
- ESP32 NTP Client-Server: Get Date and Time (Arduino IDE)
setup()
In the setup(), we initialize Wi-Fi so that the ESP32 can connect to the internet to connect to the NTP server.
initWifi();Then, call the initTime() function and pass as argument the timezone String. In our case, for Lisbon/PT timezone.
initTime("WET0WEST,M3.5.0/1,M10.5.0"); // Set for Lisbon/PTAfter that, print the current local time.
printLocalTime();loop()
In the loop() show the local time for ten seconds.
Serial.println("Lets show the time for a bit. Starting with TZ set for Lisbon/Portugal");for(i=0; i<10; i++){ delay(1000); printLocalTime();}If at any time in your code you need to change the timezone, you can do it by calling the setTimezone() function and passing as an argument the timezone string. For example, the following lines change the timezone to Berlin and display the time for ten seconds.
Serial.println();Serial.println("Now - change timezones to Berlin");setTimezone("CET-1CEST,M3.5.0,M10.5.0/3");for(i=0; i<10; i++){ delay(1000); printLocalTime();}Then, we go back to our local time by calling the setTimezone() function again with the Lisbon/PT timezone string variable.
Serial.println();Serial.println("Now - Lets change back to Lisbon and watch Daylight savings take effect");setTimezone("WET0WEST,M3.5.0/1,M10.5.0");printLocalTime();To check if daylight saving time is taking effect, we’ll change the time to 10 seconds before the winter time takes effect. In our case, it is on the last Sunday of October (it might be different for your location).
Serial.println();Serial.println("Now change the time. 1 min before DST takes effect. (Last Sunday of Oct)");setTime(2021,10,31,0,59,50,0); // Set it to 1 minute before daylight savings comes in.Then, show the time for a while to check that it is adjusting the time, taking into account DST.
for(i=0; i<20; i++){ delay(1000); printLocalTime();}After this, let’s change the time again to check if it changes to summer time when it comes the time. In our case, it is on the last Sunday of March.
Serial.println("Now change the time. 1 min before DST should finish. (Last Sunday of March)");setTime(2021,3,28,1,59,50,1); // Set it to 1 minute before daylight savings comes in. Note. isDst=1 to indicate that the time we set is in DST.Show the time for a while to check that it is adjusting to the summer time.
for(i=0; i<20; i++){ delay(1000); printLocalTime();}Demonstration
Now, let’s test the code. After inserting your network credentials, upload the code to your ESP32.
After that, open the Serial Monitor at a baud rate of 115200 and press the ESP32 RST button to start running the code.
First, it shows your local time with the timezone you’ve set on the code.
After that, it will change to the other timezone you’ve set on the code. In our case, we set to Berlin.
After that, you should see the change to winter time. In our case, when it’s 2 a.m., the clock goes back one hour.
We also check if it adjusts to summer time when it comes the time. In the example below, you can see that the clock goes forward one hour to set summer time.
Wrapping Up
This quick tutorial taught you how to set timezone with daylight saving time using the setenv() and tzset() functions.
We hope you found this tutorial useful. We have other tutorials related to time that you may like:
- ESP32 NTP Client-Server: Get Date and Time (Arduino IDE)
- Getting Date and Time with ESP32 on Arduino IDE (NTP Client)
- ESP32 Data Logging Temperature to MicroSD Card (with NTP time)
Learn more about the ESP32 with our resources:
- Build Web Servers with ESP32 and ESP8266 eBook
- Learn ESP32 with Arduino IDE (eBook + video course)
- More ESP32 tutorials and projects…
Thank you for reading.
