#define INTERVAL1 5000
#define INTERVAL2 7000
#define INTERVAL3 9000

unsigned long millis_1 = 0;
unsigned long millis_2 = 0;
unsigned long millis_3 = 0;

void displayTime(unsigned long);
void setup() 
{
    Serial.begin(9600);
}
void loop() 
{
  if(millis() > millis_1 + INTERVAL1)
  {
    millis_1 = millis();
    displayTime(millis_1);
    Serial.println("1");
  }
  if(millis() > millis_2 + INTERVAL2)
  {
    millis_2 = millis();
    displayTime(millis_2);
    Serial.println("2");
  }
  if(millis() > millis_3 + INTERVAL3)
  {
    millis_3 = millis();
    displayTime(millis_3);
    Serial.println("3");
  }
}
void displayTime(unsigned long time_millis)
{
    Serial.print("Time: ");
    Serial.print(time_millis/1000);
    Serial.print("s - ");
}