Update: I wrote an e-mail to Michael, who originally wrote the tutorial, and here's his reply:
Yes, way down in the footnotes its noted Test::Tutorial is using Date::ICal 1.31 which is horribly out of date. I haven't really touched it in four years. I put up a post on perl-qa to see if anyone wants to take on the job of bringing it up to date.

In reply to Re^4: Strange result for example in Test::Tutorial. by BioGeek
in thread Strange result for example in Test::Tutorial. by BioGeek

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