Why does Proton Calendar not sync on iPhone?
Most "Proton Calendar not syncing" reports are not a sync failure at all — they're a structural gap. Proton Calendar runs as its own end-to-end encrypted app and does not write events into the iPhone's native Calendar database (EventKit), so anything created in Proton never shows up in Apple's Calendar app, on Apple Watch faces, or in any third-party app that reads from the system calendar store.
That separation exists because of how Proton encrypts data. Events, titles, and attendee details are encrypted client-side before they leave the device, which is a different model from the plaintext CalDAV records that iCloud or Google expose to the native iPhone Calendar app. Two calendars that never talk to each other will look broken even when both are updating fine on their own.
Can you add Proton Calendar as a CalDAV account on iPhone?
No — Proton does not publish a CalDAV endpoint that the iPhone's built-in Calendar app can connect to directly, the way iCloud or a self-hosted CalDAV server does. Apple's own setup path for outside calendar servers expects a hostname, port, and principal URL for a CalDAV account, and Proton doesn't hand out those credentials for consumer use.
The closest workaround is exporting a read-only ICS link and subscribing to it from Settings, but a subscribed calendar is one-way and refreshes on Apple's own schedule, not instantly. Compare that to how Google exposes a CalDAV interface for its own calendars — Proton has no equivalent for third-party clients, which is why it sits closer to Outlook's setup pattern than iCloud's.
How do you fix Proton Calendar app sync problems on iPhone?
Inside the Proton Calendar app itself, the fix is usually connectivity, authentication, or a stale cache — not a server outage. Confirm Wi-Fi or cellular data is active, force-quit and reopen the app, then check that Background App Refresh is on for Proton Calendar in iPhone Settings.
If events still lag, sign out and back into the Proton account inside the app; expired session tokens are a common cause of silent sync stalls. This mirrors the same checklist Apple gives for any account that stops updating: check the account toggle, then the fetch schedule, since accounts without push support only update on a timer rather than instantly.
Do Proton Calendar events trigger real alarms on iPhone?
No — Proton Calendar sends standard local notifications from inside its own app, not AlarmKit alarms, so they get muted by the Silent switch and by Focus the same way any other app notification does. AlarmKit, introduced with iOS 26, is a separate system that rings through Silent mode and Focus, but only apps built on it get that behavior.
Pealo connects to Google Calendar, Outlook, and the iPhone's own Calendar, turning those events into system alarms — it does not connect to Proton directly. A workaround some people use is subscribing to Proton's ICS feed as an iPhone Calendar subscription, which then surfaces inside the iPhone Calendar connection Pealo reads from, though the one-way refresh delay still applies. Details on how that connection behaves are in alarms for iCloud and local iPhone calendars, and the full setup lives at pealo.app.
How does Proton Calendar compare to iCloud and Google for sync?
Proton Calendar trades native iPhone integration for end-to-end encryption, while iCloud and Google both expose standard protocols the iPhone already understands. The table below lines up the practical differences for someone deciding where to keep events.
| Capability | Proton Calendar | iCloud | Google Calendar |
|---|---|---|---|
| Native CalDAV account on iPhone | No | Yes | Yes |
| Push updates to system Calendar | No | Yes | Yes |
| Shows in Apple Watch calendar faces | No | Yes | Yes |
| Direct Pealo alarm connection | No | Yes | Yes |
| End-to-end encrypted by default | Yes | No | No |
Teams juggling more than one of these sources often end up with the same missing-event symptoms on the Google side too — the underlying cause is almost always which calendar the event actually lives in, not a broken sync engine.
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