The current time can be read with the second(), minute(), and hour() functions. In this example, sin() and cos() values are used to set the position of the hands.


void setup() {
 size(200, 200);
 stroke(255);
 smooth();
}
void draw() {
 background(0);
 fill(80);
 noStroke();
 // Angles for sin() and cos() start at 3 o'clock;
 // subtract HALF_PI to make them start at the top
 ellipse(100, 100, 160, 160);
 float s = map(second(), 0, 60, 0, TWO_PI) - HALF_PI;
 float m = map(minute() + norm(second(), 0, 60), 0, 60, 0, TWO_PI) - HALF_PI;
 float h = map(hour() + norm(minute(), 0, 60), 0, 24, 0, TWO_PI * 2) - HALF_PI;
 stroke(255);
 strokeWeight(1);
 line(100, 100, cos(s) * 72 + 100, sin(s) * 72 + 100);
 strokeWeight(2);
 line(100, 100, cos(m) * 60 + 100, sin(m) * 60 + 100);
 strokeWeight(4);
 line(100, 100, cos(h) * 50 + 100, sin(h) * 50 + 100);
 
 // Draw the minute ticks
 strokeWeight(2);
 for (int a = 0; a < 360; a+=6) {
   float x = 100 + ( cos(radians(a)) * 72 );
   float y = 100 + ( sin(radians(a)) * 72 );
   point(x, y);
 }
}