RGB Code ATTiny85

const int RED=4;
const int GREEN=0;
const int BLUE=1;
const int SENSE=3;
const int threshold=4;
const int rate=120;
boolean dark=false;
float cycle_time=float(rate)*768/3600000.0; //rate*768 is ms in rainbow, 3600000.0 is ms in hour
float timeout_hours=8; //must be divided by x.0 (e.g. "1/15.0")to get accurate result if not an integer
int cycles_to_run=int(timeout_hours/cycle_time)+1;
int cycle_counter=0;

void setup() {
  pinMode(RED,OUTPUT);
  pinMode(GREEN,OUTPUT);
  pinMode(BLUE,OUTPUT);
  changeColor(0,0,0);
}

void loop() {
  if ((analogRead(SENSE)<threshold)&&(!dark)) {
    dark=true;
  }
  else if ((analogRead(SENSE)>=threshold)&&(dark)) {
    dark=false;
    cycle_counter=0;
  }
  if ((dark)&&(cycle_counter<cycles_to_run)) {
    for (int i=0;i<256;i++) {
      changeColor(255-i,i,0);
      delay(rate);
    }
    for (int j=0;j<256;j++) {
      changeColor(0,255-j,j);
      delay(rate);
    }
    for (int k=0;k<256;k++) {
      changeColor(k,0,255-k);
      delay(rate);
    }
    cycle_counter++;
  }
  else {
    changeColor(0,0,0);
    delay(50);
  }
}

void changeColor(int r,int g,int b) {
  analogWrite(RED,255-r);
  analogWrite(GREEN,255-g);
  analogWrite(BLUE,255-b);
}