[mbrubeck]

About a month. Threes! came out on February 6 [1], while 2048's git repository started on March 5 [2] and the game was first published about a week after that.

[1] http://www.theverge.com/2014/2/6/5361708/threes-ipad-iphone-...

[2] https://github.com/gabrielecirulli/2048/commit/f4d95b66723cd...