strange timing with setTimeout

Is it possible you have some other interval or setWatch running in the background that could be keeping it really busy? Maybe try a reset(1) to be sure?

From a board I just tried:

>for(var i = 0; i < 10; i++) {var dt = new Date();setTimeout(function(){console.log(new Date() - dt);},1000);}
=undefined
992.88940429687
994.90356445312
996.18530273437
997.86376953125
999.1455078125
1000.42724609375
1002.01416015625
1003.44848632812
1004.73022460937
1010.58959960937

>var dt = new Date();setTimeout(function(){console.log(new Date() - dt);},100);
=1
101.13525390625
>var dt = new Date();setTimeout(function(){console.log(new Date() - dt);},100);
=1
101.25732421875
>var dt = new Date();setTimeout(function(){console.log(new Date() - dt);},100);
=1
101.13525390625
>var dt = new Date();setTimeout(function(){console.log(new Date() - dt);},100);
=1
101.13525390625
>var dt = new Date();setTimeout(function(){console.log(new Date() - dt);},100);
=1
101.13525390625


>function tst(duration){
:  var pnt = 0;
:  function tstTimeout(){
:    var dt = new Date();
:    setTimeout(function(){
:      console.log(new Date() - dt);
:      if(pnt++ < 4) tstTimeout();
:    },duration);
:  }
:  clearTimeout();
:  tstTimeout();
:}
=function (duration) { ... }
>tst(1000);
=undefined
1001.55639648437
1001.67846679687
1001.52587890625
1001.52587890625
1001.46484375

So all that looks pretty good. You'd expect the ~1ms delay because of the time taken to parse and execute setTimeout after the initial Date variable is created.