Why is May 25th Geek Pride Day? ThinkGeek has answers.

It's 2 anniversaries and one sci-fi reference.

Star Wars opened on this day in 1977, Douglas Adams died on this day in 2001, and it's a holiday in Discworld by Terry Pratchett.

Of course, this part applies to me, as ThinkGeek explains:

If you're reading this, odds are every day
is Geek Pride day for you.