If you click on your name in a topic, you get a drop down menu. One of the choices is "View Public Profile", which will show your profile and the date you joined.
You joined on the 22nd, so by Thursday or Friday you should be able to. If I recall, you have to wait until it's 20 days exactly, to the hour, so if you signed up at 11pm, you'd have to wait til 11pm on Day 20.
Hope that helped!