Honestly, I couldn't say exactly. It had to be around 1992-ish, when I went to the Ritz at the mall down in PA and picked up a used K1000. I used that camera for about four years until it seized (in hindsight, it was probably just a bad battery contact) and shelved it.
I graduated to an Olympus digital point and shoot that lasted all of about 6 months before breaking (protip: don't tie camera operations to whether a flimsy plastic door is slid left or right 'cause when that door breaks, the camera is toast). Went a few years without, and picked up a Kodak EasyShare something-or-other, then picked up a Canon Powershot A470 (best camera for the cost I ever had. Seriously. Especially after I was able to hack it with a third party firmware that allowed for RAW and bracketing etc on it). When that eventually went down to sensor issues (and overuse), I grabbed another Kodak. Much less exciting than the first had been.
By this point a combination of wanting something more like my K1000 combined with my wife getting pregnant with my first son led me to picking up a new K-x, and I was Pentax 'reborn' so to speak.
I managed to get a few thousand shots of my son before I eventually managed to kill the K-x by improper lens cap usage (lint gets on lens mount, lens gets mounted, lint gets in guts of camera, camera goes PFFFT). This was right about the time when my wife became unexpectedly pregnant with our second child, so I immediately budgeted 2 grand to get a new camera and a 'nice' lens of some sort for when taxes rolled around again. In the meantime I picked up a Samsung 'WiFi' camera. Great concept, but the IQ was just not there after coming off the K-x.
So I was reborn a third time a few months ago with the K-30 and a Sigma 10-20mm and I've been quite happy since, especially as I can take some really decent photos of the littler guy.
First shot I took with the K-x...
Very first shot with the K-30...
This of course means that as soon as I make plans to buy whatever camera Pentax comes out with to replace the K-5 (or the mythical FF should it come to be), my wife'll wind up pregnant so I have to continue this tradition for a third child. :-/