// How many underscores has __DATE__
// Reference:
//   https://gcc.gnu.org/onlinedocs/cpp/Standard-Predefined-Macros.html
//

void setup() 
{
  Serial.begin(115200);

#if defined(_DATE_)
  Serial.println("It is with one underscore:");
  Serial.print("_DATE_ = ");
  Serial.print(_DATE_);
  Serial.print(", _TIME_ = ");
  Serial.println(_TIME_);
#elif defined(__DATE__)
  Serial.println("It is with two underscores:");
  Serial.print("__DATE__ = ");
  Serial.print(__DATE__);
  Serial.print(", __TIME__ = ");
  Serial.println(__TIME__);
#elif defined(___DATE___)
  Serial.println("It is with three underscores:");
  Serial.print("___DATE___ = ");
  Serial.print(___DATE___);
  Serial.print(", ___TIME___ = ");
  Serial.println(___TIME___);
#endif

}

void loop() 
{
  delay(10);
}