+Provide a sane syntax for date ranges. First, we don't want to require
+both endpoints to be specified. For example it would be nice to be
+able to say things like "since:2009-01-1" or "until:2009-01-1" and
+have the other enpoint be implicit. Second we'de like to support
+relative specifications of time such as "since:'2 months ago'". To do
+any of this we're probably going to need to break down an write our
+own parser for the query string rather than using Xapian's QueryParser
+class.
+