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Proton Calendar

What it is

Proton Calendar is a privacy-focused, end-to-end encrypted calendar service developed by Proton (the makers of Proton Mail).

What problem it solves

It provides a secure and private way to manage schedules and events without exposing data to service providers or third-party advertisers. It ensures that your itinerary remains confidential even from the service provider.

Where it fits in the stack

Orchestration / Personal Information Management. It serves as a secure alternative to cloud calendars like Google Calendar or Outlook.

Typical use cases

  • Confidential Scheduling: Managing sensitive personal or business schedules.
  • Secure Invitations: Sending and receiving encrypted event invitations.
  • Team Coordination: Sharing calendars within a secure ecosystem.
  • Cross-platform Sync: Synchronization across web, Android, and iOS.

Security Model

Proton Calendar uses several layers of protection: - End-to-End Encryption (E2EE): Event titles, descriptions, locations, and participants are encrypted on the client side before being sent to Proton's servers. - Zero-Access Encryption: Proton cannot decrypt your data; they only store the encrypted blobs. - Signed Events: Prevents tampering with event data during transit or at rest.

Getting started

Account Setup

  1. Create a Proton account at proton.me.
  2. Access the calendar via the web interface or mobile app.

Data Migration

To import existing calendars: 1. Export your calendar from Google or Outlook as an .ics file. 2. In Proton Calendar, go to Settings > Import. 3. Upload the .ics file.

Integration Patterns

Proton Bridge

While Proton Calendar does not support native CalDAV for third-party apps directly, users often use the Proton Bridge (primarily for Mail) as a proxy. For Calendar specifically, native CalDAV support is a highly requested feature but currently limited.

Exporting for External Use

You can generate a "Secret Link" to share your calendar in a read-only format with other applications that support iCal: 1. Go to Settings > Calendars. 2. Select the calendar and click Share. 3. Copy the Secret Link.

CLI / Automation Options

Official CLI support for Proton Calendar is currently absent. However, users can interact with encrypted data via community tools or the official Bridge for related services.

Conceptual: Importing via .ics (CLI)

You can use standard CLI tools to prepare and manage calendar data before uploading:

# Combine multiple ICS files for import
cat calendar1.ics calendar2.ics > combined.ics

# Verify ICS structure before import
grep "BEGIN:VEVENT" combined.ics | wc -l

Strengths

  • Privacy: E2EE for all major event fields.
  • Security: Strong authentication (2FA/Security Keys) and data protection.
  • Transparency: Client-side code is open source and regularly audited.
  • No Ads: Data is not scanned for advertising purposes.

Limitations

  • Limited Integration: No direct CalDAV support for desktop apps like Apple Calendar without third-party workarounds.
  • Automation Gap: Lack of official API or CLI tools for programmatic event management.
  • Features: Fewer advanced scheduling features compared to Google Calendar.

When to use it

  • When privacy and data security are the top priorities.
  • If you are already integrated into the Proton ecosystem (Mail, Drive, VPN).
  • For managing highly sensitive appointments or legal/medical schedules.

When not to use it

  • If you require deep integration with many third-party automation tools (Zapier, Make, etc.).
  • If you need native CalDAV access for legacy desktop calendar applications.

Sources / references

Contribution Metadata

  • Last reviewed: 2026-05-19
  • Confidence: high