Allow apps to use your calendar information
Some apps and websites can use your calendar information to provide you with services and features. For example, an app might use your calendar to help you set up an event or a reminder. See Control access to your calendar.
To authorize an app or a website to use information from your calendar, click OK in the dialog. If you don’t want to authorize the use of your calendar information, click Don’t Allow.
If you allow third-party apps or websites to use your calendar information, any information they collect is governed by their terms and privacy policies. It’s recommended that you learn about the privacy practices of those parties.
You can review and change your privacy settings using the Privacy pane of Security & Privacy preferences.
Choose Apple menu > System Preferences, click Security & Privacy, then click Privacy.