Special days can be used to celebrate and they can also act as a marker to note what has happened in the past year. So what use would a 'PM day' be? I can think of a few ways it could be useful:

• Perl hackers could set up a 'social' meeting of their local Perl Mongers group to celebrate Perl Monks. We could also contact other monks or other Perl Mongers groups in the area and have a bigger get-together;
• A date marker like New Years to say, 'What have I done on PM in the last year?', 'Do I have goals for Perl advocacy?', 'Did I hit my XP goal for the year?', etc.
• A day to tell other people about Perl Monks;
• A day of reflection: where is Perl Monks today, what has happened in the last year, what goals does the site have for the next year?
• Maybe serve as a date for people taking new site responsibilities or passing them on. This would allow people to take roles for a set time.
• And of course another big day for the gift-card industry as the inevitable flood of Perl Monks cards, computer toys, and other paraphernalia hits the market;

So I think there are lots of fun reasons to have a special day.

Now as for when, Dec. 23 might make for less participation due to some other things happening that time of year. I think I like the July 11 idea.