Everybody uses Google Calendar (well, most people), and it's a tool many of us probably rely on every day to manage our lives, our work, and all the things we'd forget if our phones didn't remind us to do them.

Google Calendar has, then, also become a repository of highly personal information about us - our doctor appointments, our social plans, our whereabouts in general, and more. And because of that, giving a loved one or a close business associate access to our calendar only makes sense, right? After all, you want your spouse to be able to put dinner plans in your calendar or your coworker to be able to edit the location of a meeting if it should change at the last minute.

Unfortunately, sharing these permissions with people on your calendar could be doing something you weren't aware of: making your private events visible to those people. And that could be giving them more information than you want. (Or, like Artem, who spotted this, have your birthday surprises ruined.)

It's not immediately intuitive that Google Calendar would work this way, but it does, and you should probably be aware - here's the basic rundown.

Anyone with "make changes" or higher permission can see - and edit - your private events

When you share your Google Calendar with someone, there are four privilege levels, as shown in the image below. Two of them allow the shared person to see your private event details, and two do not. You can probably guess which, but anyone with the "make changes" or "make changes and manage sharing" permission can also see and edit calendar events marked "private."

This may not seem intuitive, but those two permissions essentially amount to administrative privileges in your calendar. A person who can edit or create events in your calendar can set them to 'private' as well, so it only makes sense (logically, not necessarily practically!) that they'd be able to see private events, too. Obviously, this isn't ideal - there should probably be a middle permission here (edit permissions with no ability to see or create private events), but this could just be a consequence of how Calendar works on the back-end, not someone at Google being lazy.

So, what are the potential solutions?

How to make sure your private events really are private

Unfortunately, both fixes here are far from ideal. The first is basically a given: you reduce the permission level of the person you've shared your calendar with. "See all event details" - despite what the name suggests - doesn't let the sharee see all event details, just those with their visibility set to the default or 'public' levels. Private events will simply show to that person as the standard "busy" block with no details, as they would if they were given "See only free/busy" permission level. That's the easiest way to address this, but it obviously means that person can no longer edit your calendar.

Google does tell you about this if you set an event to "private" on the web, but curiously, no such warning appears in the mobile app. Now you know.

The second option is to create a new calendar. This is also inconvenient for a number of reasons - for example, I often frequently put things in my personal calendar before realizing I meant to put them in my work calendar - and it's definitely more work. Unfortunately, it's the only real way to have your cake and eat it here, which is to say, to give the "edit" level permission to someone on your primary calendar and also have a place to put events where they won't be seen by that person. Or, you can create a new, shared calendar with the idea being all of the events involving that person go in the new calendar, and you keep your personal stuff private (or set to one of the two read-only permissions) - either approach would obviously work.

As I said, neither solution is great, but there you go.

Google doesn't do a great job of making this obvious when you share a calendar, but the facts are buried down a ways in this support article under the "Control what others can see" heading in the "Permission settings" subheading. See below (highlight by us).

Make changes AND manage sharing

  • Change sharing settings
  • Add and edit events
  • See details for all events, including private ones
  • See the time zone setting for the calendar
  • Permanently delete the calendar
  • Restore or permanently delete events from the calendar's Trash

Make changes to events

  • Add and edit events
  • See details for all events, including private ones
  • See the time zone setting for the calendar
  • Restore or permanently delete events from the calendar's Trash

So, there you go. It's not great, but it's what we have, and it's definitely something you should be aware of if you're sharing your Google Calendar with someone else.