Board Thread:Game Discussions/@comment-81.147.140.179-20140827014444/@comment-25055391-20140827141559

Typically it has been about two weeks yes. However, they also mixed in the Blazestone for 3k gems from chest during one of those cycles, also the new update has stated a new "Guaranteed Reward" chest, which could mess with the timing again. So in general, yes, every two weeks, but we don't know til the event pops up.