manually pass an epoch on ESP dev board

/*
 * Manually set human readable time on an ESP device
 * Sketch will work on both ESP8266 and ESP32
 * The idea of the sketch is to show how an EPOCH Unix time can be passed to
 * the ESP's time function which is enabled by default when you select the board
 * To do this you press the Flash/Boot button on the controller and enter the
 * blocking "Serial Input" mode
 * enter a valid EPOCH value and the system will sync to it.
 * I have also changed the default 1/1/1970 Epoch to 1/1/2021 Midnight plus 2hrs 13min 20sec
 * You need to chage the "TZ_INFO" line 18 to suit your timezone
 * You can find the zone list here <https://github.com/nayarsystems/posix_tz_db/blob/master/zones.csv>
 */

#if defined (ARDUINO_ARCH_ESP8266)
    #include "sntp.h"
#endif

#define BTN 0
#define TZ_INFO "NZST-12NZDT,M9.5.0,M4.1.0/3"     //for local time

int32_t epoch = (1609459200 + 8000);         //1st Jan 2021 00:00:00 [UTC] + 2hrs 13min 20sec
bool pressed = 0, btnState, lastBtnState = 1, enableSerial = 0;
uint32_t previousTime = 0;
uint8_t lastSec;

void updateTime(void){              //This is the method to produce a
    uint8_t sec = 0;                //Human readable clock in the Serial monitor
    char buf_t[80];
    time_t t = time(NULL);
    struct tm *now_tm;
    now_tm = localtime(&t);
    sec = now_tm->tm_sec;
    if(lastSec != sec){
        strftime(buf_t, 80, "\n[%Z][UTC %z] %c", now_tm);
        Serial.println(buf_t);
        lastSec = sec;
    }
}

void setup() {
  Serial.begin(115200);
  setenv("TZ", TZ_INFO, 1); tzset();                   //Setup your Timezone for local time
  #if defined (ARDUINO_ARCH_ESP8266)
    struct timeval _tv = {.tv_sec = epoch};            //passing epoch to timeval
    settimeofday(&_tv, NULL);
    Serial.println("\n\nESP8266 Epoch is Set and clock is starting\n");
  #elif defined (ARDUINO_ARCH_ESP32)
    struct timeval tv = {.tv_sec = epoch};             //passing epoch to timeval
    settimeofday(&tv, NULL);
    Serial.println("\n\nESP32 Epoch is Set and clock is starting\n");
  #endif
}

void loop() {
     btnState = digitalRead(BTN);

    if(btnState != lastBtnState){
      pressed = 1;
      previousTime = millis();
    }
    if(millis() - previousTime >= 50){
      if(pressed){
        if(btnState == 0){
          enableSerial = 1;
          Serial.println("\n\rSerial is Waiting for a Unix Epoch Value\n\r");
        }
      }
      pressed = 0;
    }
    if(enableSerial){
      if(Serial.available() > 0){
        String inString = Serial.readStringUntil('\n');
        epoch = inString.toInt();
          #if defined (ARDUINO_ARCH_ESP8266)
            struct timeval _tv = {.tv_sec = epoch};            //passing epoch to timeval
            settimeofday(&_tv, NULL);
          #elif defined (ARDUINO_ARCH_ESP32)
            struct timeval tv = {.tv_sec = epoch};            //passing epoch to timeval
            settimeofday(&tv, NULL);
          #endif
        enableSerial = 0;
        Serial.println("\n\rSystem Human Readable Clock has been Updated\n\r");
      }
    }else{
      updateTime();
    }
    lastBtnState = btnState;
}