unsigned long prev_time = 0;
unsigned long curr_time = 0;
int period = 1000;
int ton1 = 1000;
int toff1 = 2000;
int ton2 = 2000;
int toff2 = 4000;

void setup(){
  Serial.begin(9600);
  pinMode(13, OUTPUT);
  pinMode(12, OUTPUT);

prev_time = millis();
}

void loop() {
  curr_time = millis();
  if ((curr_time - prev_time)> ton1){
    digitalWrite(13, LOW);
    //prev_time = curr_time;
  }
  if ((curr_time - prev_time)> ton1+toff1){
    digitalWrite(13, HIGH);
    //prev_time = curr_time;
  }

   if ((curr_time - prev_time)> ton2){
    digitalWrite(12, HIGH);
    //prev_time = curr_time;
  }
  if ((curr_time - prev_time)> ton2+toff2){
    digitalWrite(12, LOW);
    prev_time = curr_time;
  }
}