In October 2017, Google announced a new web user interface (UI) for Google Calendar. As a reminder, they have several options for how their users will transition to this new UI.
On January 8th for Rapid Release domains (and January 15th for Scheduled Release domains), we’ll begin auto-upgrading users whose domains are set to the automatic (default) rollout option.
In this phase, users will still have the option to opt out of the new UI until February 28th, 2018, when all users will be fully upgraded.
Any individual users who had manually opted out of the new web UI previously will not be upgraded until February 5th.
Additionally, while this opt-out phase does not impact domains whose admins have selected a manual rollout, users in these domains will still be upgraded to the new UI on February 28th, 2018, with no option to opt out.