Transform.rotation is setting local rotatoin

I am trying to preserve an objects world rotation through parenting it. I am using this code to do that

 function OnTriggerStay(other:Collider){
     var tmp : Vector3 = this.transform.rotation.eulerAngles;
     this.transform.SetParent(other.gameObject.transform.parent.parent);
     this.transform.rotation.eulerAngles = tmp;
 }

But this is just setting the local rotation to what the objects world rotation was before the parenting. Which is confusing me because I though transform.rotation set the world rotation.