AH, from a design functionality standpoint, any information entered should be usable in some way. Not sure if a calendar is going to be the first result of such a thing, but perhaps the ability to sort a personal collection view by date purchased ascending/descending. Of course, that would require that the purchase date field is actually filled out on the collection entry.
In other words, we allow for the storage of the data but currently provide no way to make use of it, on the site, without exporting the data.