Hi
You can indeed use intervals in the format 'FROM-TO', f.ex. '2012-07-13-2012-07-14' for the 13th to the 14th. You can also leave out either the from or to, like '-2012-07-13' or '2012-07-13-'.
It is a bit hard to read with the from/to divider being the same as the date-parts divider (-), but it works :)
Christian