Calendar Sync Utility is a macOS application that keeps your schedule visible in one place. It reads the events on your own Google Calendar and copies them into a calendar you select in Apple Calendar on your own Mac, then keeps that copy up to date as your Google Calendar changes. Optionally, it can also write to a Google calendar you own: copying events into it, or placing "busy" holds on it for the times you are busy on another of your calendars.
Using it takes three steps: sign in with your Google account, grant read-only calendar access, and choose the Apple Calendar the events should be copied into. From then on the application runs quietly in the menu bar and keeps that calendar in sync automatically.
At sign-in the application requests two things from Google: read-only
access to your calendars (the calendar.readonly scope), used
solely to read the events you chose to copy or to hold time for, and your
account's email address, used solely to show which account is signed
in.
Only if you choose a Google calendar as the place to write does the
application ask, in a separate consent, for access to events on the
calendars you own (the calendar.events.owned scope). It
uses that access solely to create, update and delete the events it
wrote there itself, each of which it marks as its own; events you or
anyone else made are never changed. It sends no invitations or update
emails.
All of your data stays on your own device. Sign-in credentials are kept in the macOS Keychain, event data is written only into the calendars you selected, and nothing is sent to any server operated by the developer — the application has none. You can revoke its access at any time from your Google Account permissions page.
See the privacy policy and terms of service for full details. Calendar Sync Utility is distributed directly by its developer.