> > the 3rd Monday in Feb
> What's the practical value of being
> able to encapsulate this into an
> atomic, machine-readable, value?
A machine-readable value would make it easier to retrieve them with high
recall, for example. Maybe there are different LCSH (or other) URI's, such
as http://id.loc.gov/authorities/sh20something that could be helpful for
such kinds of dates.