Google is adding Gemini panel to Google Calendar
At the moment, Gemini in Google Calendar is still being tested, and it is unknown when more users will have access to it.

Google now testing a new Gemini panel in Google Calendar to help users manage their schedule. Gemini allows users to quickly and easily view their meetings, add new events, and check details of events that are already scheduled.
This feature is designed to help users to work with the calendar in a more convenient way. It saves time by eliminating the need to search for or add events manually. Users can instead use Gemini's voice assistant features to complete tasks more quickly.
To access Gemini's calendar features, users can click on the "Ask Gemini" icon in the upper-right corner of the Google Calendar window. From there, they can choose from a list of suggested queries or create their own. For example, Gemini can analyze a schedule and suggest adding a meeting or lunch to a free time. Also, the assistant can find already scheduled events in the calendar.
This feature is available as part of early access testing program, Google Workspace Labs.
Gemini sidebar is now available in Gmail, Google Drive, Docs, Sheets, Slides and Chat. At the moment, Gemini in Google Calendar is still being tested, and it is unknown when more users will have access to it.