One calendar on your Mac for every Google account, and Apple's

Click Calendar on Koi's dock and the calendar opens in the middle of your screen: the week to begin with, or the month, with the day you pick beside it. Each thing takes its kind's colour, the way Google Calendar does it: Events are blue (calls, meetings and classes), Tasks are gold (to-dos and follow-ups you tick off) and Appointments are pink.

Click one to see it: its time, its reminder, its Meet call, which calendar it's on and its description, with a pencil to edit it and a bin to delete it. In the week, things at the same time sit side by side, laid out as Google Calendar lays them out.

Click New, double-click a day, or click an empty hour in the week, and the new thing starts at the half hour you clicked. Drag down a day to pick a stretch of time, and you see it on the grid as you go.

The editor is laid out like Google Calendar's: the title, the kind, the day with its start and end (and how long that is), All day, Add guests, a description and files, then Cancel and Done. A new thing gets its kind's usual reminder.

When a reminder comes due, and again as the thing starts, Koi's dock says so in a card with Open and Snooze, which waits five minutes. It plays a sound unless you've turned Koi's sounds off.

Koi's own reminders stay in Koi. Nothing goes to the Mac's Calendar, Reminders or notifications, and the dock tells you so.

Tap Fn + ⌘ and say it: “remind me to call mum at six”, “set a timer for twenty minutes”, or “put the investor call in my calendar for Friday at 3pm New York time”. Koi adds it, and it can tick things off, move them and open them too. Something Koi only thinks belongs on your calendar shows in the dock instead, for you to add with a click.

Ask “what's on today?” or “what's due?” and Koi answers from its own calendar, plus Google Calendar and the Mac's Calendar and Reminders when they're connected.

Talking to Koi is a call with an AI, so it goes online while the call lasts. A question about your day sends that day's events along with it, and they're kept nowhere. The calendar itself stays on your Mac. More on Koi, the AI assistant that sees your screen.

A time is kept as the moment and the zone it was given in. “3pm New York time” shows in your Mac's own time, with New York's beside it when the two differ. A whole day stays on its date wherever your Mac is.

Connect Google Calendar in Settings, Connections, or from the foot of the calendar's day. Add as many Google accounts as you have, each with its own sign-in. Each one is listed by its address, with its own Disconnect and Add another account under them.

Every calendar from every account shows beside Koi's own, each with its own switch. A meeting you're invited to on two accounts, or a calendar shared between them, shows once. Google events are refreshed every five minutes and whenever the calendar opens, and each one says which Google calendar it's on.

Change one in Koi's editor (its title, day, time or description) or delete it, and the change goes straight to Google, unless it's on a calendar you can only see. The dock reminds you of a Google event when Google would remind you on screen. Sign out of Koi, or uninstall it, and every Google account is disconnected, with Koi's access taken back at Google too.

Click Add guests and type their addresses: Return, a comma or a space adds one. As you type, Koi suggests people you've invited before and people on your Google events. With the first guest, the event goes on Google with a Google Meet link, from the Google account you pick, and Google emails each guest the invitation.

Their answers show in the editor and on the event's card: Going, Maybe, Not going or Invited. Change or delete an event with guests and Google tells them. An event with a Meet call has Join with Google Meet on it.

Ask by voice and Koi fills in the editor for you to check, and nothing goes until you press Done. Each address Koi filled in says where it came from until it's sent: Koi's guess, From your Contacts, or As Koi heard it.

Connect Apple Calendar and Apple Reminders in Settings, Connections, each after macOS asks. Every calendar on your Mac shows, iCloud's and those of any account you've added to the Mac's Calendar app, and every reminder with a date shows as a task you can tick off in Koi.

Change one in Koi's editor and the change goes through macOS, which syncs it as it always does. A Google event that's also in the Mac's Calendar, because you added the same Google account there, shows once. Calendar and Reminders keep alerting as usual and Koi's dock doesn't, so nothing alerts twice.

Pick or drop files on the editor's paperclip line. On Koi's own things they're copied into Koi's data folder on your Mac, open with a click, and go when the thing is deleted.

On a Google event they're uploaded to your Google Drive and attached there. Koi can reach only the files it puts in your Drive, and a file you take off a Google event stays in your Drive.

When a recorded call ends and you say yes to its notes, Koi offers the dates the call agreed on, each ticked, to add to your calendar or leave out. More on recording calls on your Mac.

A few minutes before a meeting your documents say something about, the dock offers Brief me. Say yes and the meeting's title, its people and the lines of your own pages about it go to Koi's AI, and a short page comes back: where things stood, what to remember, what to ask. Koi reads the calendar for this only when macOS already lets it, and Brief me is a switch in Settings, under Koi.

Koi's own calendar and its reminders stay on your Mac, in the same place as your documents. Files attached to Koi's own things are copies on your Mac and are never uploaded, unless you invite people or add a Meet call. Then the thing moves to your Google Calendar, and its files to your Google Drive.

Google Calendar goes only between your Mac and Google, never through our server, and each Google sign-in is kept in your Mac's Keychain. Apple Calendar and Reminders are read on your Mac through macOS. Events from both, from a month back to half a year ahead, are held in memory while Koi runs and aren't written to Koi's database.

What you add in Koi stays in Koi, unless you invite someone, or ask Koi by voice to put it in Google Calendar, Apple Calendar or Reminders. Changing your Google or Apple calendars by voice needs “Let Koi use my Mac for me” on. By voice, Koi moves a Google or Apple event, but never deletes one.

• It's on your Mac only. Koi has no iPhone app, and its own calendar doesn't sync anywhere. Google and Apple keep your events in their calendars synced, as they always have.
• Its own reminders show only in Koi's dock, not in Notification Center or on your phone.
• There are no booking or scheduling links.
• Outlook and Exchange calendars show only through the Mac's Calendar app, if you've added the account there.
• It isn't sold on its own. It comes with Koi, which needs a plan.

If a calendar is all you want, our list of the best Google Calendar apps for Mac covers free options like Notion Calendar and the Mac's own Calendar.

Yes. The calendar comes with Koi on every plan, along with unlimited dictation and recorded calls: Pro, at $20 a month or $192 a year after a 3-day free trial that needs a card, or Lifetime, paid once: $59 for the first 25 buyers, rising to $199. There's no free plan.

Clicking around the calendar costs nothing extra. Asking Koi by voice is a call with Koi, which counts as Koi usage. See the plans.