How can a day be declared a "month"? Very easily, if you ask devotees of the Dadaists. (By the way, April 1 is one of 13 days that received this designation.)
Read the mayor's proclamation. It's quite amusing. Yes, it's a bit silly, but at least you get the impression that the mayor knew he was doing something silly. And it's no more silly than this Virginia county's decision to declare the first week of May '05 as "Respect for Law Week."
On the other 51 weeks of the year, I guess it was anything goes.