This is Aaron from the Cooper-Hewitt [1,2].
I've been lurking for a couple months, after discovering the work being done here, and just digesting the conversation. I wanted to briefly stick my head up and say hello and ask what if any discussion there's been about the ability to query ranges of dates in EDTF ? And specifically, how it is or would be implemented (at the brass tacks level).
I ask because it's very much germane to the work we're doing around the collection  and eventual re-opening of the museum in 2014. Currently we've got a finite list of "periods"  without explicit dates associated with them and a variety of "display dates" associated with individual objects that I've been able to block out in to something that we can sorta-kinda use for doing date queries on the set of things. 
One of the things I've been tossing around, since getting to the CH, is some way to boil (with an emphasis on the boil-iness of boiling) a date down to a number. Specifically something that can be stuck in a database and operated against without the need for (insert some library or other software that I don't have or can't run). Numbers are awesome because all computers support them!
The slightly longer version was discussed a while back on the Historic OpenStreetMap mailing list:
I realize that Julian dates might in fact be a better solution but one of the things I would like to avoid doing is shifting the meaning of "zero" (relative to time) yet again. Fixing 0 to the Unix Epoch might seem a bit arbitrary because it is but it has the advantage of playing nicely with the robots.
Anyway, it's all still wet paint in my mind so I'd curious to know what has been discussed about searching EDTF ranges or pointers to stuff I can read up on.
 http://collection.cooperhewitt.org/periods/ <-- we will probably ask an intern to at least mark these up in EDTF soon, if nothing else