unsigned long interval=1000;
unsigned long previousMillis=0, millis2=0; 
bool ledState = 0, led2 =0; 
unsigned long currentMillis;

void setup() {
pinMode(13, OUTPUT);
digitalWrite(13, ledState);
pinMode(12, OUTPUT);
digitalWrite(12, led2);
}
 
void loop() {
currentMillis = millis(); 

if (currentMillis - previousMillis >= interval) 
 {  
  ledState = !ledState; 
  digitalWrite(13, ledState); 
  previousMillis = currentMillis;
}

if (currentMillis - millis2 >= 1500) 
 {  
  led2 = !led2; 
  digitalWrite(12, ledState); 
  millis2 = currentMillis-500;
}

}