Arduino:
날짜를 문자열로 변환하기

#include <Wire.h>
#include <RTClib.h>

RTC_DS3231 rtc;

void setup() {
  Serial.begin(9600);

  if (!rtc.begin()) {
    Serial.println(F("Couldn't find RTC"));
    while (1);
  }

  if (rtc.lostPower()) {
    Serial.println(F("RTC lost power, let's set the time!"));
    // Following line sets the RTC to the date & time this sketch was compiled
    rtc.adjust(DateTime(F(__DATE__), F(__TIME__)));
  }
}

void loop() {
  DateTime now = rtc.now();

  char dateStr[11];
  snprintf(dateStr, sizeof(dateStr), "%04d-%02d-%02d", now.year(), now.month(), now.day());
  Serial.println(dateStr);

  delay(1000);
}