User blog comment:Brandon Rhea/New Page and Article Headers: Official Release Date/@comment-31702336-20170613113136/@comment-20644-20170613144124

It wasn't postponed. As other users mentioned here, "the week of June 12th" meant it could have been anytime this week, and since code releases happen on Tuesdays and Thursdays it meant either June 13th or June 15th.