it being a problem with the script is what I was afraid of.
Looking at it more closely, I was wrong. There is likely a problem in the template coding... actually several.
1. When you click on the 17th and then one of the [more details] links on that page, part of the link URL contains
calendar.pl?
datestring=2009081717&selected_datestring=20090817...
Note the datestring= value in the URL has too many digits (although it still looks to function that way).
2. To display the correct event date when linking from the main 'Events for August 2009' display,
you'll have to pass the correct event date in the links to the events as a datestring= value. Otherwise it looks like your template uses the selected_datestring= value (if set like from clicking on a calendar grid date) or it uses the current date.
Someone likely needs to correct the coding of the template you're using.
JMO
Dan O.