If I were preparing to file a design patent around early May 2015, I might have held-off a bit on the filing to pass the May 13, 2015 threshold. Design patents stemming from applications filed on or after that date have a 15-year patent term (calculated from patent issuance) as opposed to a 14-year term for those filed prior to the threshold date.
When I looked at the numbers, I was surprised to find that the extra year did not capture the hearts of design patent filers as I might have expected. (See Chart below.) Yes, filings on the 13th of May were above average and the preceding two days were below average, but the first look here that few filers acted to game that extra year.