From the module Spreadsheet::ParseExcel I recall Window uses seconds since 1904 ... i would test the number to see if that is you cause. Specific readme this was in is here.
OH, a sarcasm detector, that’s really useful
Well, when you dereference the date field it looks like you are getting a date/time, though not in an immediatly recognizable format. I know that excel stores it's date in some strange format, have you looked into how access stores dates?
There's got to be an excel module on cpan that will work with dates. Maybe the date manipulation provided there will work with your access date problem.