I've stumbled upon many posts on G+ and FB (example) that state that December 15th is some sort of official Otaku Day.

I've also found this page which is from 2012, which means this was celebrated, at least, in 2012 too.

However, I found no reliable pages that say that this is a thing, much like the person who posted the first post on this forum.

I found this ANN article that puts this year's Otaku Day on August 17th (2012's was on the 18th). Furthermore, the second link provided there links to a Facebook page, in which it is stated that this event takes place on the third Saturday of August every year.

The event announced on the first paragraph is, apparently, called "World Otaku Day". The one announced on the second is the "(Annual) International Otaku Day". However, I find no reference of any of these two, nor of any "official" Otaku day on Wikipedia.

So, is there a day that is really (official, or something of the sort) regarded as Otaku Day? Are there any more reliable sources that have a fixed date for this event?

Or are these two events relatively official and both recognised as two different Otaku days?