PublicationEvent for quarterlies and other odd cases

Hi folks,
  Looking at the PublicationIssue and PublicationEvent, I'm confused as to where to put the cover date and how to represent dates that don't map directly to the ISO format.  Quarterlies are the most obvious, but bi-monthlies and semi-monthlies are other examples.  I'm also confused as to whether this should be in "datePublished" (as a date) or "publication" (as a PublicationEvent, which could indicate a quarter by giving a startDate and endDate of the relevant months, perhaps?).
  I don't see an example of anything other than a fully specified date- is there a more comprehensive set of date examples somewhere?  Defining a PublicationEvent that spans the whole time designated by the cover date seems to be the most flexible option, but perhaps that is stretching the concept of "Event" too far.
  "releasedEvent" seems like the clear home for the actual release date(s), which are easier as they are full dates.
thanks,-henry