https://arstechnica.com/gadgets/2017/09/apple-watch-users-can-download-watchos-4-on-september-19/

CUPERTINO—Apple revealed details about watchOS 4, its newest update to the Apple Watch's operating system, back at June's WWDC keynote. Now we know when the update will be pushed to the public: September 19. This comes on the heels of Apple announcing the Apple Watch Series 3 model with standalone LTE service at today's event as well.

WatchOS 4 will change the look and feel of the Apple Watch slightly with aesthetic updates, a new vertical app dock, and a few redesigned apps. The Music app has an entirely new look in watchOS 4, the Workout app has a new color scheme as well as more "tap and go" button options, and the News app can now be used receive headlines on your wrist and save articles for later reading.