How do you make an Accurate Timer on iphone

I’ve been using the following to count time accurately on the iphone.
I want something to happen every .1 seconds. Is this the best way to do it?

var playtime=0.0;

In the update loop

playtime+=Time.deltaTime;

if(playtime>.1){
 playtime=0;
    playFrame();
 }

That isn’t very accurate because you are setting playTime = 0 inside your test - ignoring the value above .1 I would suggest:

 if(playtime > 0.1) {
      playtime -= 0.1;
      playFrame();
 }