I'd suggest having a look at the Goid Relations ontology http://wiki.goodrelations-vocabulary.org/Quickstart - it's aimed at businesses but the OpeningHours specification might do what you need http://www.heppnetz.de/ontologies/goodrelations/v1.html#OpeningHoursSpecification
While handling public holidays etc is not immediately obvious it is covered in this mail http://ebusiness-unibw.org/pipermail/goodrelations/2010-October/000261.html
Picking up on the previous comment Good Relations in RDFa is one of the formats Google use for Rich Snippets and it is also picked up by Yahoo
On 7 Jun 2011, at 23:05, Tom Keays <[log in to unmask]> wrote:
> There was a time, about 5 years ago, when I assumed that microformats
> were the way to go and spent a bit of time looking at hCalendar for
> representing iCalendar-formatted event information.
> Not long after that, there was a lot of talk about RDF and RDFa for
> this same purpose. Now I was confused as to whether to change my
> strategy or not, but RDF Calendar seemed to be a good idea. The latter
> also was nice because it could be used to syndicate event information
> via RSS.
> These days it seems to be all about HTML5 microdata, especially
> because of Rich Snippets and Google's support for this approach.
> All three approaches allow you to embed iCalendar formatted event
> information on a web page. All three of them do it differently. I'm
> even more confused now than I was 5 years ago. This should not be this
> hard, yet there is still no definitive way to deploy this information
> and preserve the semantics of the event information. Part of this may
> be because the iCalendar format, although widely used, is itself