set a time and see red flash 5 seconds later.

time_demo_v2.pde

// Time Demo
// set a time and see red flash 5 seconds later.
// v 0.2
// Includes text on screen
// Steve is the best
// It seems he can do anything.
// March 23, 2017

int startTime = 0;
int currentTime = 0;
int endTime = 15000;


void setup() {
    size(250, 250);
}

void draw() {
    background(25);
    println("startTime: "+startTime);
    println("currentTime: "+currentTime);
    println("endTime: "+endTime);
    currentTime = millis();
    
    if (currentTime >= endTime){ // if we get to the endTime....
      startTime = currentTime; // it resets itself!!
      endTime = currentTime + 5000; // another 5 seconds
      background(255,0,0);
    }
    
    text("CURRENT TIME: " + (currentTime/1000), (width/5*1), height/2-15);
    text("START TIME: " + (startTime/1000), (width/5*1), height/2);
    text("END TIME: " + (endTime/1000), (width/5*1), height/2+15);
}

void keyPressed() {
    if(key == 'r'){
      // println("millis: "+millis()); // show me the time!
      startTime = currentTime;
      endTime = currentTime + 5000; // another 5 seconds      
    }
}