The next Apple operating system OS X 10.11 (aka El Capitan) will appear on 30 September, 2015. Before the date was officially announced on the company’s website, Apple had snuck it to the public in advance.
How you ask?
On the Keynote for iPhone 6s, Apple demonstrated, the 3D touch function using email as an example. What was in that email? A call for September 30, 2015 to be regarded as the shipping date for El Capitan.
Apple has since confirmed 30 September following the keynote as the official release date on the Apple website.