Mistwell
Crusty Old Meatwad
By "fan writer" I assume you mean published writer who researched the date laboriously and narrowed it down to the 21st. It wasn't just some wild guess, actual effort was made.
He said it was a guess. If you think he's a good source, then you have your answer.
Even if we are celebrating "the year", it's a third over and we haven't seen a lot of festivity. We're unlikely to see anything until July when the starter set comes out. So half the anniversary is gone. Most people won't get the core books until September. That's assuming they release them all at once and don't stagger the releases.
You cannot actually celebrate for an entire year, because then it becomes meaningless. You pick some time during that year, and you celebrate the anniversary. You can maybe stretch it for a month or two, but you can't do it for 365 days. And I still have no idea why you'd want to.
Anyone who hears about the game in the intervening period will have some difficulty getting into the game. There's no easy on ramp right now. Anyone who hears about the 40th, or watched Community and is thinking D&D is SoL.
When I think back at 2014 it won't be "the year of D&D". It will be "the year with less D&D than any other year since its creation." Well... since 1978 maybe.
First, this year has seen the most amount of free material probably ever, from the official D&D company. Anyone who wanted to get into the game, could do it for free by simply downloading the rules, and then participating in numerous free adventures they sent out, and giving feedback, and taking part in the many discussions that happened this year. This year has seen a huge resurgence in D&D discussion on boards like this very one. For me, it's been an awesome D&D year so far.
Second, why do you care that every day be celebrated as the 40th anniversary? Why is this important? As long as it is celebrated some time this year, why is it meaningful to you that it be right now?