Accuracy difference between getTimer and date.getTime

[INDENT]I came accross another issue regarding the accuracy between the getTimer and date.getTime functions.
I use this simple script (AS2)


var tObj:Object = new Object();
tObj.startDate = new Date();
tObj.startDateTime = tObj.startDate.getTime();
tObj.startTimer = getTimer();

var gTimerID:Number;
gTimerID = setInterval(this, "checkT", 100);

 function checkT() {
    tObj.msTimer = getTimer()-tObj.startTimer;
    var my_date:Date = new Date();
    tObj.msDateTimer = my_date.getTime() - tObj.startDateTime;
    tObj.diffTime = Math.abs(tObj.msTimer-tObj.msDateTimer);

What happens if you let this simple app running is that the trace will show that the difference between the getTimer and date.getTime results slowly increases.
I would assume some inaccuracy, but not one that would slowly increase during the lifetime of the application.
The reason I want to compare the two values is that I want to see if someone is tampering with the application speed with a program such as Cheat Engine. And I noticed the date.getTime function isn’t affected by that program, but the getTimer function is.