Currently I can make API calls to the effect of "show me all games that will be released in August 2014". I've noticed a few erroneous dates, however. For example, Hyrule Warriors shows up in my above call with a date of August 14th, yet the game doesn't release in North America until September 26th (it seems it just grabs the first release date out of all regions). Release date information for all regions is stored by Giant Bomb (http://www.giantbomb.com/hyrule-warriors/3030-44782/releases/) but is not exposed via the API.
It would be nice to have something along the lines of:
A simpler alternative would have the API accept a region code (NA, JP, etc.) and use that for the release date filtering.