OnePlus had announced some time ago that their next product launch would take place in New York on October 30th. However, Apple has just taken that same date to release their new Macs and iPad Pro. The Chinese company has responded by moving their own event up one day.
https://www.notebookcheck.net/OnePlus-has-changed-the-6T-s-launch-date-because-of-Apple.340696.0.html