EDIT (16 Sep): Based on the community feedback, we have made one further change: each Atlantis event will start on Thursday and end on Saturday.
Beginning this month, the duration for the Atlantis Rises Event has changed. It will now last 3 days instead of 4. September’s Atlantis Rises Event is scheduled to begin on Thursday, 26th of September, 2019 and lasts until Saturday, 28th of September. This is due to upcoming new features and extended duration of the updated Challenge Events.
Thank you for your understanding and best of luck in the battles!