A new validator for iCalendar

In January 2009 I wrote a series of entries [1, 2, 3] documenting examples of ill-formed iCalendar files. And I argued that we need an analog, in calendar space, to the incredibly useful RSS/Atom feed validator.

I’m delighted to report that Doug Day has taken up the challenge. The first incarnation of his validator is up and running at http://icalvalid.cloudapp.net. It’s based on Doug’s DDay.iCal, which is the same .NET-based iCalendar class library used by the elmcity aggregator. But, like the RSS/Atom validator, it’s driven by an extensible and language-independent suite of tests.

The validator reports numerical scores for an iCalendar file, and gives advice about how it will be handled by popular calendar applications. Some examples:

The Keene High Varsity Basketball schedule scores a 96.25: “This calendar has minor problems, but will likely work correctly in major calendar applications.”

The Hannah Grimes Center’s calendar, based on Drupal, scores 92.5: “This calendar has moderate problems, but may work correctly in major calendar applications.”

The Keene Chamber of Commerce calendar scores 0: “This calendar has severe problems; very few (if any) applications will accept this calendar.” (DDay.iCal does, in fact, overlook these problems, and does parse events from this calendar.)

I’m hugely grateful to Doug Day for doing this important work. Although calendars seem to be ubiquitous, familiar, and interoperable, the examples I’ve been collecting in the wild show that, even though the standard has been around for over a decade, the iCalendar ecosystem is still very immature. This validator will help that ecosystem evolve.

The validator itself, of course, will also evolve. You can send feedback to Doug at the address given on its home page. If you’re curating a location or a topic using the elmcity service, you can email me about problem calendars or bring them to the curators’ room.

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