Get the time from the internet on ESP32, ESP8266 and Arduino with a time API

Short answer: an ESP32, ESP8266 or Arduino with Wi-Fi can get the current local time from the internet with one HTTPS request. The response already has the time zone offset and daylight saving applied, which NTP does not give you.

// GET https://api.timelogicapi.com/api/timezone/America/New_York?api_key=YOUR_KEY
// -> {"utc_offset":"-04:00","timezone":"America/New_York","datetime":"...","unixtime":...,"dst":true, ...}

NTP or a time API: which should my sketch use?

Many projects use both: NTP to keep the clock ticking, and one API call at boot (or once a day) to learn the zone and offset. More detail in NTP vs a time API.

ESP32: get the local time and set the clock

#include <WiFi.h>
#include <WiFiClientSecure.h>
#include <HTTPClient.h>
#include <ArduinoJson.h>
#include <sys/time.h>

const char* WIFI_SSID = "your-ssid";
const char* WIFI_PASS = "your-password";
const char* API_KEY   = "YOUR_KEY";

bool syncTime() {
  WiFiClientSecure client;
  client.setInsecure();  // quick start; use client.setCACert(rootCA) in production
  HTTPClient http;
  http.begin(client, "https://api.timelogicapi.com/api/timezone/America/New_York");
  http.addHeader("X-API-Key", API_KEY);
  int code = http.GET();
  if (code != 200) { Serial.printf("HTTP %d\n", code); http.end(); return false; }

  JsonDocument doc;  // ArduinoJson 7
  DeserializationError err = deserializeJson(doc, http.getString());
  http.end();
  if (err) return false;

  struct timeval tv;
  tv.tv_sec = (time_t)doc["unixtime"].as<long>();
  tv.tv_usec = 0;
  settimeofday(&tv, nullptr);  // system clock now holds UTC
  Serial.println(doc["datetime"].as<const char*>());  // local time with offset
  Serial.println(doc["dst"].as<bool>() ? "DST in effect" : "standard time");
  return true;
}

void setup() {
  Serial.begin(115200);
  WiFi.begin(WIFI_SSID, WIFI_PASS);
  while (WiFi.status() != WL_CONNECTED) delay(250);
  syncTime();
}

void loop() {
  time_t now = time(nullptr);  // keeps counting after the sync
  Serial.println((long)now);
  delay(10000);
}

To use the device's own location instead of a fixed zone, request /api/ip instead of /api/timezone/America/New_York; the zone is resolved from the public IP address the request comes from.

ESP8266

#include <ESP8266WiFi.h>
#include <ESP8266HTTPClient.h>
#include <WiFiClientSecureBearSSL.h>

void printTime() {
  std::unique_ptr<BearSSL::WiFiClientSecure> client(new BearSSL::WiFiClientSecure);
  client->setInsecure();  // quick start; pin a certificate for production
  HTTPClient https;
  https.begin(*client, "https://api.timelogicapi.com/api/timezone/Europe/Berlin.txt?api_key=YOUR_KEY");
  if (https.GET() == 200) Serial.println(https.getString());
  https.end();
}

Parse the .txt response without a JSON library

String body = http.getString();               // from a .txt URL
int i = body.indexOf("unixtime: ");
long unixtime = body.substring(i + 10, body.indexOf('\n', i)).toInt();

The .txt form lists the same 15 fields as key: value lines in alphabetical order, so unixtime: is always present.

Which fields does the response carry?

datetime (local, with offset), utc_datetime, unixtime, utc_offset, raw_offset and dst_offset (seconds), dst, dst_from, dst_until, abbreviation, timezone, day_of_week (0 = Sunday), day_of_year, week_number (ISO) and client_ip. Full table: WorldTimeAPI-compatible routes.

Prefer the /v1 API? GET /v1/time/current?tz=America/New_York returns unix, unix_ms, iso_local and the weekday names; see the current time reference.

Tips for devices

• Sync, don't poll. One request at boot and one every few hours is plenty; the RTC keeps time in between. 10,000 free requests a month is roughly one request every 4 to 5 minutes from a single device.
• Keep the key out of public repos. Put it in a secrets.h that is not committed.
• Handle failures. If the request fails, keep running on the last synced time and retry later.

Related guides

• Raspberry Pi and MicroPython (Pico W)
• Migrating a worldtimeapi.org sketch
• Timezone from an IP address
• World Time API guide (pillar)