For the longest time I never knew that you could customize the date keywords for created, published and updated. But, it is super easy using PHP Date keywords, where X is the PHP Date character:
%asset_created_X% %asset_updated_X% %asset_published_X%
So, using %asset_created_F% %asset_created_j%, %asset_created_Y% would produce something like, February 11, 2009. Great to use in asset listings or anywhere that the default keywords for these don't cut it.