[Utah-astronomy] When is Astronomy Day?

We all know that the little SLAS Star Party handouts has the incorrect date for Astronomy Day.  If I remember correctly, it is supposed to be on May 2, which this site seems to confirm; http://www.astroleague.org/al/astroday/astrofacts.html   But then I get on the Clark Planetarium site and find a different date, which is found on the last page of this pdf layout: http://www.clarkplanetarium.org/DATA/NEWSLETTERS_IMAGES/March%202008.pdf   Interesting to see that astronomers aren't sure when Astronomy Day really is.