I use Japanese sites to determine the dates:
beatmania IIDX 7th style release date listed here: http://ja.wikipedia.org/wiki/Beatmania_IIDX DDRMAX2 release date listed here: http://pastport.jp/timeline/compare/c91d6f4ec5d1a5c298a7c8360cbfa3b2 --M.B. (talk) 03:02, 4 May 2014 (UTC)