I find myself on occasion still adding "2009" to my dates, despite this being the third month of 2010, and I think it is because my brain cannot fathom the fact that we have reached a year in humanity that was essentially relegated to science fiction.
I'm sure Twain and Edison and Churchill felt something similar in 1900, but there was still something antiquated about the change. There were still so many basic mysteries about life and the universe to be discovered - the electron was found only three years earlier - and they must have known that there were entire worlds of thought and science and culture that would never be approached in their lifetimes.
But today, I feel that anything is possible, and may come at any time. When it was 1989 or 1996 or even 2005, it was still the present, but today I have the slightest suspicion that we are living in the future.
And so sometimes when I write "2009", I don't correct it.