Let's see what you are quibbiling about here. Desert Shield and the buildup for Desert Storm lasted from, say, mid-August to late February, when the ground attack commenced. About six months. Now, how much time has expired since Sepember 2002? October, November, December, January, February, March. Hmmm - seems like six months to me.
Time for you to take off your mittens when you need to perform complex calculations...
President G W H Bush did not wait for a UN resolution to start military movement.