View as Markdown

Sharing your calendar

Calendite's sharing has no accounts, no sign-up, and no server that can read your events. This page explains how to use it, and exactly what does and doesn't happen to your data, so you can check the claims above.

Pairing with another person is Android only for now. On iOS the option shows a "not available here" screen. Both phones must be on the same Wi-Fi to pair. Linking your own browser, below, is a separate feature and works from any device today.

Pairing with someone

More → Share calendar. Three options: Invite Someone, Been Invited?, and Use Calendite On A Computer.

The flow, in person:

  1. You tap Invite Someone. Your phone shows a QR code and starts advertising on the local network. (There's a typed code as a fallback, but it's 24 characters: an emergency exit, not the main path.)
  2. They tap Been Invited? and scan it.
  3. Both phones now show the same six digits. Compare them out loud.
  4. Both of you tap They Match. This is a hard gate: nothing has moved yet, and the calendar key isn't sent until both sides confirm. If the digits differ, tap They Don't Match and nothing has happened.
  5. You name them. The name is stored on your device only and never transmitted.
  6. A first sync runs.

The six-digit check is the security of the whole thing. It's what makes it impossible for someone to interpose themselves between the two phones: they'd have to make two different key exchanges produce the same six digits.

After pairing

Their events appear under their name, and are read-only to you. Yours appear on theirs. An event's page says whose it is.

An event can also go on their own calendar, as one of their events, if you choose it for that event: see Putting an event on someone's calendar.

The tag filter grows a segmented control letting you look at your events or theirs.

To stop: More → Share calendar → People You Share With → remove them. That purges their events, revokes their device, rotates the calendar key and dissolves the shared mailbox.

Putting an event on someone's calendar

Each event has a People row. It decides who can see the event and, person by person, whose own calendar it lands on, so a date night can go on both your calendars without landing on your calendar with everyone else you share with.

An event you put on someone's calendar arrives as one of theirs: it sits among their own events, takes their tag of the same name if they have one, and sets off their own default reminder rather than yours. If they have no matching tag, it arrives without one.

They can hide it or decline it. Hide takes it off their calendar on their phone only, and Show It Again brings it back. Decline takes it off and lets you see that they declined; Add It Back undoes that. The People row on your event shows who has declined, and ticking their calendar again sends it back.

Calendite warns you before it clashes. Putting an event on someone's calendar names every one of theirs it collides with, and on how many dates, before you confirm.

Only your own calendar sets off your reminders. An event that's on your calendar only because someone shared it with you no longer trips your default countdown.

Hiding individual events

On an event's People sheet, untick Can see it for someone and the event is hidden from them. They get its start, end and duration, nothing else, and see it as Alice Is Busy only where it overlaps something on their own calendar.

This is stronger than the equivalent in other apps: for a hidden event, only the timing is ever encrypted under the shared key. The title, location and everything else are never sent in any form. A modified client on their end has nothing to decrypt. The hiding is enforced by cryptography, not by their app choosing to respect a flag.

Also: everything you created before pairing never travels at all, regardless of settings.

Syncing when you're not together

By default, sharing syncs only when both phones are on the same network. That's the Same network only setting.

If you want it to work when you're apart, choose a sync server at More → Settings → Sync Server:

Choice What it means
Same network only (default) no server involved at all
The Calendite relay our server holds sealed blobs until the other phone collects them
Your own deployment the same, on infrastructure you control

What a sync server can and can't see

If you enable one:

It cannot see: your events, titles, times, locations, notes, tags, the names you gave people, or any encryption key. Everything it stores is sealed, and it has nothing to open it with.

It can see: the traffic shape, meaning that some mailbox received some data of some size at some time, and 16-character device identifiers.

It holds data only until every device has collected it, then drops it.

Access to a mailbox is by knowledge of its address, which is derived from the calendar key. Only members can compute it.

The encryption, briefly

Every change is encrypted twice, under independently derived keys: ChaCha20-Poly1305 and then AES-256-GCM. Breaking one leaves you facing the other.

Key agreement is hybrid post-quantum: X25519 (classical) combined with ML-KEM-768 (lattice). An attacker has to break both, so recording traffic today in the hope of decrypting it with a future quantum computer doesn't work. Signatures are likewise Ed25519 and ML-DSA-65, with both required.

On your phone, keys are wrapped by hardware-backed storage (StrongBox where the device has it).

Alerts and notes are deliberately never shared. Your partner sees the event, not your reminders about it or what you wrote.

How the encryption works covers all of this properly, including what it doesn't protect against.

Limitations

  • Revocation protects the future, not the past. What someone already synced is on their device. Removing them stops what comes next.
  • Async invites (sharing a link for someone to accept later) are recognised but not yet redeemable. The app will tell you to ask for a live code instead.

Using Calendite in a browser

More → Share calendar → Use Calendite On A Computer links a browser to your phone, similar to WhatsApp Web: go to web.calendite.com, scan the code it shows with your phone, and your calendar appears in the browser and stays in step. Change something on either one and the other follows: events, tags, alerts, and anything you've marked done.

The browser's copy is locked, not just synced. Each time you come back, your phone unlocks it with one scan. Nothing about your calendar is kept on a server in a form anyone else can read.

You can use a browser and share with a person at the same time. The browser gets a calendar of its own, under its own key, so the people you share with can never read what's sent to it. A change you make in the browser reaches the people an event is shared with, exactly as if you'd made it on your phone. Events other people put on your calendar stay on your phone for now, and don't yet appear in the browser.

Linked devices

You can link more than one browser, such as a laptop and a work computer. Each stays in step with your phone and with every other linked browser.

More → Linked Devices lists each one: which browser it is, when it was last open, and when you last unlocked it. Give one a name you'll recognise, like Work Laptop.

Left a computer unlocked? Lock Now locks it the next time it checks in; it needs your phone to unlock again. Unlink This Browser gives your calendar a fresh key: the browser you removed wipes what it held and can never read your calendar again, and your other devices carry on as normal.

Linking a new device is part of Calendite Plus. A device you've already linked keeps working if your plan ends, and you can always see and unlink your devices without Plus.

Next