Arduino ESP32 時計合わせ

//Time
struct tm timeinfo;
String dateStr;
String timeStr;
String dispTime;

// Time
void getTimeFromNTP() {
  char  ntpServer[] = "ntp.jst.mfeed.ad.jp";
  const long gmtOffset_sec = 9 * 3600;
  const int  daylightOffset_sec = 0;
  configTime(gmtOffset_sec, daylightOffset_sec, ntpServer);
  while (!getLocalTime(&timeinfo)) {
    delay(1000);
  }
}
void GetTime() {
  getLocalTime(&timeinfo);
  char buf1[3], buf2[3], buf3[3];

  sprintf(buf1, "%02d", timeinfo.tm_mon + 1);
  sprintf(buf2, "%02d", timeinfo.tm_mday);

  dateStr = (String)(timeinfo.tm_year + 1900)
            + "/" + (String)buf1 + "/" + (String)buf2;
  sprintf(buf1, "%02d", timeinfo.tm_hour);
  sprintf(buf2, "%02d", timeinfo.tm_min);
  sprintf(buf3, "%02d", timeinfo.tm_sec);

  dispTime = (String)buf1 + ":" + (String)buf2;
  timeStr = dispTime + ":" + (String)buf3;
  //Serial.println(dateStr + timeStr);

}