I have tons of free time...I clicked on someone's profile and backspaced their name/member number and replaced it with 1, then 2, then 3 until I found a member that was still active. And the profile shows the "join" date also.
Your member number is 87243. One of several ways to find it.... when you are looking at one of your posts, click on your avatar, click on your user name in that popup window, and then look at the address bar in your browser...