int lightVal = 0;
int lightPin = A0;
int luxVal = 0;
int LEDpin = 10;
int buttPin = 9;
unsigned long millTime = 0;
void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600);
  pinMode(lightPin, INPUT);
  pinMode(LEDpin, OUTPUT);
  pinMode(buttPin, INPUT_PULLUP);

}

void loop() {
  // put your main code here, to run repeatedly:
  unsigned long millTimeStart = millis();
  while(digitalRead(buttPin) == 0)
  {
    millTime = millis() - millTimeStart;
  }
  if(millTime > 0)
  {
    Serial.print("millTime = ");
    Serial.println(millTime);
  }
  millTime = 0;
  

}