Summary
Gemini can only currently view your primary calendar and the birthdays calendar. Additional calendars created in Google Calendar, or shared with you in Google Calendar cannot be accessed by Gemini.
It'd be great if Gemini got access to these calendars as well, at the very least the additional ones that you own.
Details
1️⃣ Problem: Gemini can currently only access your primary calendar. This can be frustrating for people who have separate calendars for work/school and personal events, or for shared calendars such as for families, clubs, etc. This is also a downgrade from Google Assistant, who has this functionality already and is being replaced by Gemini.
Allowing Gemini to access all calendars that Google Assistant can will solve this issue.
2️⃣ Proposed Solution: Gemini should be able to access any calendars that Google Assistant currently can. In Google Assistant settings within the Google app, there is is an option to select both the default calendar, and which calendars Google Assistant has access to. This list includes secondary calendars and shared calendars.
For Gemini, you could either directly use the setting from the Google Assistant settings, or you could design a dedicated settings page just for Gemini that works in a similar way.
3️⃣ Benefits: This would be great for people who separate their work events from their personal ones. When they ask Gemini what events they have today, it can respond with both work events and personal events. This will help with planning and scheduling.
It's also great for students who put their classes or due dates in separate calendars, so they can know what classes they have from Gemini.
Shared calendar access will also be great for the family, so you can check if your spouse is working tomorrow, for example.