But even  isn’t particularly relevant to web designers. What really matters is when browsers supporting features. We began using parts of CSS 2.1 as soon as browsers started shipping with support for those parts. If we had waited for every browser to completely support CSS 2.1 before we started using any of it, we would still be waiting.
It’s no different with HTML5. There won’t be a single point in time at which we can declare that the language is ready to use. Instead, we can start using parts of the specification as web browsers support these features.
Remember, HTML5 isn’t a completely new language created from scratch. It’s an evolutionary rather than revolutionary change in the ongoing story of markup. If you are currently creating websites with any version of HTML, you’re already using HTML5.
Honestly, if you at all confused about the various dates and timescales and recommendations about HTML5 (which some people at the W3C aren’t helping), you should buy this book just for the first couple of chapters (the rest of it’s good, too).