.endTime()

Returns the time at which the animation will finish according to the parent timeline’s local time. This does factor in the timeScale. For example:

var tl = gsap.timeline();
var tween = gsap.to(e, {duration: 1, x: 100}); //create a 1-second tween
tl.add(tween, 0.5); //insert the tween at 0.5 seconds into the timeline
console.log(tween.endTime()); //1.5
tween.timeScale(2); //double the speed of the tween, thus it'll finish in half the normal time
console.log(tween.endTime()); //1