NTP Time Stamp V2 (uses a String)

//NTP Serial monitor time stamp print by making a String to the format desired

#include <WiFi.h>
#include <WiFiUdp.h>
#include "time.h"

String      time_str;
uint32_t    previousTime = 0;
const char* ssid     = "YOUR SSID HERE";
const char* password = "YOUR WIFI PASSWORD";

//NTP TZ_INFO for Auto Zone and Daylight savings Offsets
// This from Github    NZST-12NZDT,M9.5.0,M4.1.0/3
// https://github.com/nayarsystems/posix_tz_db/blob/master/zones.csv
const char* NTP_SERVER = "pool.ntp.org";
const char* TZ_INFO    = "NZST-12NZDT,M9.5.0,M4.1.0/3";

WiFiClient client; // wifi client object

void setup() {
  Serial.begin(115200);
  if (!StartWiFi(ssid,password))
  Serial.println("Failed to start WiFi Service after 20 attempts");;

  /* configTime(12*3600, 0, "pool.ntp.org"); // +1hour (1*60*60=3600=+1hour) ahead for DST in the UK */
  configTime(0, 0, NTP_SERVER); // if TZ configured
    setenv("TZ", TZ_INFO, 1);   // for TZ and Daylight Auto change
  time_t now = time(nullptr);
  delay(2000); // Wait for time to start
  while (!update_time());  //Get the latest time
  previousTime = millis();
}

void loop() {

  if(millis() - previousTime >= 1000){
    while (!update_time());
    previousTime = millis();
  }

}

bool update_time(){
  time_t now = time(nullptr);
  struct tm *now_tm;
  int hour,min,second,day,month,year;
  now = time(NULL);
  now_tm = localtime(&now);
  hour = now_tm->tm_hour;
  min  = now_tm->tm_min;
  int weekday = now_tm->tm_wday;
  String week_days[] = {"Sun","Mon","Tue","Wed","Thu","Fri","Sat"};
  String wday = week_days[weekday];
  second = now_tm->tm_sec;
  day    = now_tm->tm_mday;
  month  = now_tm->tm_mon + 1;
  year   = now_tm->tm_year - 100;// YY only no CC element add 1900 for CC element too
  // Needs to be in the format HH:MM:SS Sat 05-07-17
  time_str = (hour<10?"0":"")+String(hour)+":"+(min<10?"0":"")+String(min)+":"+(second<10?"0":"")+String(second)+" "+wday+(day<10?" 0":" ")+String(day)+"-"+(month<10?"0":"")+String(month)+"-"+String(year);
  Serial.println(time_str);
  return true;
}

int StartWiFi(const char* ssid, const char* password){
  int connAttempts = 0;
  Serial.println("\r\nConnecting to: "+String(ssid));
  WiFi.begin(ssid, password);
  while (WiFi.status() != WL_CONNECTED ) {
    delay(500);
    Serial.print(".");
    if(connAttempts > 20) return false;
    connAttempts++;
  }
  Serial.print("WiFi connected\r\nIP address: ");
  Serial.println(WiFi.localIP());
  return true;
}