Timelapse Countdown Timer in After Effects

Question

I'm sure someone out there must have done this before, but how do I create a countdown timer with hours, minutes and seconds that starts from a specific time and counts down at 71.928x speed?

71.928x because I took one frame every 3 seconds and I'm playing it back at 23.976fps.

I've tried using text expressions but to no avail.

Answer 1

You will have to do it with expressions, unfortunantly it is the only outside of possibly finding a 3rd Party plugin...

This is a good start, http://www.motionscript.com/design-guide/up-down-clock.html

Answer 2

Here's what I did in the end (as an expression on the text layer)

countspeed = 144;
clockStart = thisComp.duration * countspeed * -1;

function times(n) {
    if (n < 10)  return "0" + n else return "" + n
}

clockTime = clockStart + countspeed * (time - inPoint);

if (clockTime < 0) {
    minus = "";  clockTime = -clockTime;
} else {
    minus = "";
}

t = Math.floor(clockTime);
h = Math.floor(t/3600);
min = Math.floor((t%3600)/60);
sec = Math.floor(t%60);
ms = clockTime.toFixed(3).substr(-3);
minus + times(h) + ":" + times(min) + ":" + times(sec)