Calendly is great — until you try to use it with Proton Calendar. The moment you click "Connect your calendar", you hit a wall. Proton requires OAuth, and handing OAuth access to a third-party scheduling tool defeats the entire point of using Proton in the first place. Here is why that matters, and what to use instead.
Proton Calendar is end-to-end encrypted. The whole model is built on the idea that nobody — including Proton itself — can read your calendar data. That is a deliberate privacy guarantee, and for many people it is exactly why they chose Proton.
Calendly, Cal.com, Acuity, and most other scheduling tools work by connecting directly to your calendar via OAuth. They read your events to find free slots, and some write back to create new ones. That requires persistent read access to your calendar — which means handing a third party the keys.
For a Gmail or Outlook calendar, you might decide that is an acceptable trade-off. For a Proton Calendar, it is not. You are essentially granting a US-based SaaS company ongoing access to the calendar you chose specifically because it is private.
"I needed to share my availability across four calendars — two work, two personal, one of which was Proton. Every scheduling tool wanted OAuth access. There was nothing that worked without it, so I built CalendarMate." — Rob, creator of CalendarMate
Every major calendar provider — Proton, Tuta, Apple iCloud, Fastmail, Google, Outlook — exposes a read-only ICS feed URL. It is a standard format, it requires no authentication to use, and it shows only free/busy information. No event titles. No attendees. No private details.
CalendarMate reads those ICS feeds directly, calculates your available slots within your working hours, and presents a clean booking page anyone can use. No OAuth. No calendar connection. No third party ever touches your calendar credentials.
You can combine multiple calendars — a Proton Calendar for personal events and a Google Calendar for work, for example — and CalendarMate merges the busy times so your booking page reflects your real availability across all of them.
| Feature | Calendly | CalendarMate |
|---|---|---|
| Works with Proton Calendar | ✗ No | ✓ Yes |
| Works with Tuta Calendar | ✗ No | ✓ Yes |
| Works with iCloud, Fastmail, CalDAV | ✗ Limited | ✓ Yes |
| Requires OAuth calendar access | ✗ Required | ✓ Never |
| Multiple calendar merging | ✓ Yes | ✓ Yes |
| Short shareable booking link | ✓ Yes | ✓ Yes |
| Booking confirmation emails + .ics | ✓ Yes | ✓ Yes |
| WhatsApp call support | ✗ No | ✓ Yes |
| Free plan available | ✓ Yes (limited) | ✓ Yes (full features) |
| Pay what you want | ✗ No | ✓ Yes |
CalendarMate works best for individuals and small teams who:
Use Proton Calendar, Tuta, iCloud, or Fastmail and have been blocked by every other scheduling tool. Care about where their data goes and do not want a US SaaS company with persistent access to their calendar. Need to share availability across multiple calendars from different providers. Want a simple, clean booking link without a monthly subscription.
It is not a full enterprise scheduling platform. There is no team round-robin, no Salesforce integration, no 47 settings menus. It is deliberately simple — a booking page that works, without the privacy compromise.
In Proton Calendar, open the calendar you want to share, go to Settings → Calendars, click the calendar name, and scroll to Other calendars can subscribe to this calendar. Copy the link — that is your ICS feed URL. Paste it into CalendarMate's calendar settings and you are done.
The same process works for Tuta (Settings → Calendar → Share), iCloud (iCloud.com → Calendar → Share icon → Public Calendar), and Fastmail (Settings → Calendars → Export).
Works with Proton, Tuta, iCloud, Fastmail, and any CalDAV calendar.
No OAuth. No calendar access. Free to use.