Ok, well there was a Photoshop 7 and maybe 8. Then I guess they started this CS business. I thought they may have bee one and the same, but perhaps they went from Photoshop 1 to 7/8, then switch to CS1-CS6. So that could be 13-14 versions. One every year or 18 months could stretch 20 years.
We've guessed 1991, 92, 95, 96, 97, 98, 99, 2001.
1993.
Final answer.
Edit: we've guessed 1988, 90, 91, 92, 93, 95, 96, 97, 98, 99, 2001.