The first day Flash died was January 27th, 2010, when Steve Jobs announced the iPad. A few months later, in his Thoughts on Flash letter, he confirmed and explained why he saw the future of the mobile web without Flash. He was hardly alone in thinking so, but it remained somewhat controversial at the time.
Since then, tens of millions of iPads have been shipped and no other tablet manufacturer or mobile manufacturer has been able to ship a device with a decent Flash implementation. However, beyond the "Steve was right" mantra and the obvious trend towards HTML5, the forthcoming death of Flash still wasn't consensual.
I think October 3rd, 2011 will be remembered as the second day Flash died, this time by the hands of its owner.
Of course Adobe will still spin Flash as a convenient solution for some use cases, which will remain true for the next few years, but they clearly announced where they want to go next, and boy, I couldn't be happier that it's towards the open web. For this, I think we can all give credit to Adobe. Few companies this size would even semi-publicly admit their technology is a dead-end and invest so heavily in a more open solution.
Big cheers to them for that.
Disclaimer: I co-founded Joshfire, a company also deeply invested in HTML5.