I just noticed a little cake icon next to my name, and hovering over it it says today is the anniversary of my join date. Clicked on my icon in the top right, but couldn’t find my join date in my profile or anywhere.
Can someone tell me where I can find that? (Just kinda wondering how long I’ve been wandering around these parts!)
If you expand the Profile summary page it shows the join date in the top left of the text. There is an expand button on the top right of the summary page to do that.
When you’re looking at your profile, there’s a gray box in the upper right that says “Expand.” Click that and it’ll show you your join date (among other things).
At least, that’s what works for me. Your mileage may vary, I suppose, depending on device and theme.
Thanks. That is so funny - that box was right there but absolutely invisible to me, until you told me about it.
20 years! 
I don’t think I ever noticed it before, until I went looking to see if I could find the answer to your question!
On my PC’s web browser, if I click your name or avatar it says your join date in a box that pops up.
(Copy-pasted from the box.)
Huh ? It says May 12, '00 on mine !
My guess is that it’s contextual, and changes depending on your time zone. I’m on the west coast of the US, you’re in the UK.
Bunch of us were bored back in May 00, huh? 
I assume @pjd was declaring that your profile says May 12 to them; pjd’s join date is May 21, '03 from what my browser is saying.
Oops. Just trying to prove exactly how clueless I can be. Need any more convincing? 