I've added a new URI space to PlaceTime.com. You can now specify Intervals of time using the Gregorian calendar like this:
http://placetime.com/interval/gregorian/1995-08-04T00:00:00Z/P1D. This represents a day starting at midnight on the 4th August 1995. I got married sometime during that day. I could probably narrow it down a bit and say I got married sometime during a single hour: http://placetime.com/interval/gregorian/1995-08-04T10:00:00Z/PT1H. The HTML and RDF representations of the PlaceTime URIs are still pretty basic but I'm trying to take it one step at a time, getting the essentials out of the way first.
In related news, I've started a mailing list for discussion of PlaceTime and its URIs. Please join if you're at all interested in representations of places and times.