According to sources with 9to5Mac.com, Apple Stores will be having an overnight on Tuesday, July 24th. This includes U.S. based and international stores. Apple OS X Mountain Lion is expected to launch in July, so it is believed that the overnight may be related to Mountain Lion being launched on July 25th to the public.
Apple is announcing their Q3 2012 earnings on July 24th. When OS X Lion was announced last year, it had a July 20th release and their earnings announcement for Q3 2011 was July 19th.
Mountain Lion will not be launching along with new hardware, so there will be less setup required. The overnight is expected to be smaller too. One of the employees told 9to5Mac that it will “basically be a few guys running around with the master image installing it on every Mac.”
Apple is also known for having Tuesday overnights so the July 24th overnight may just be a coincidence. OS X 10.8 Mountain Lion will be sold as a $19.99 upgrade and will be available on the Mac App Store on the launch day.