Google Calendar:
Users will see a promotional message giving them the ability to opt in to Calendar’s new look and this will roll out gradually over a few days. If users do opt in, they can always revert to the classic look in their settings by clicking on Use the classic look.

We’ll keep you updated on when these changes will become the default for scheduled domains, and there’s more information on the new look at http://whatsnew.googleapps.com/new-look.

Release track:
Scheduled*

Editions included:
Google Apps, Google Apps for Business, Government and Education

For more information:
http://www.google.com/support/calendar/bin/answer.py?answer=1351806

New look on the way for Gmail, Calendar, Docs and Sites! Find out more at whatsnew.googleapps.com/new-look