Google has announced the dates when G Suite customers will begin getting the new Google Calendar. To this point, G Suite admins have been able to manually force the update on domains or to delay the release of the new Material Design calendar on their domains. Now that is changing with several key dates coming up.
For domains that are in the Rapid Release schedule, users will start getting update next Monday, January 8th if their domain is set to automatic updating. Users can still opt out, for now. For those domains in the Scheduled Release bracket, you will get the update following Monday, January 15th. Again, users can opt out for now.
Admins are encouraged to start rolling out the new Google Calendar as all users, regardless of domain, will have the new look come February 28, 2018. That is when the ability for users and domains to opt out of the new look will be removed.
For non-G Suite users of Calendar, the same holds true for you. If you have opted out of the new look calendar to this point, you will get moved to it on February 28th like everyone else.
Google rolled out the updated look to Google Calendar back in October after months of testing.