Comparison

Proton Calendar vs Pi Epsilon

Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.

Head to head
About

Proton Calendar

This app helps you manage your schedule with privacy in mind. It offers various viewing options, reminders, and recurring event creation. All your data is protected by end-to-end encryption and strict Swiss privacy laws, ensuring your personal information is not tracked or harvested.

Highlights
  • Agenda and day view
  • View and reply to invites
  • Automatic event addition from email
  • Light and dark mode
  • Multiple reminders
  • Recurring events
  • Cross-device sync
Features
Read full description

A calendar is a record of your life: Proton Calendar helps keep it private. Make the most of your time - See your upcoming events as you like with agenda or day view - View and reply to invites - Events and invites are automatically added to your calendar from your Proton Mail inbox - View your schedule in light or dark mode - Add multiple reminders for your events - Create recurring events on a daily, weekly, monthly, yearly, or custom basis - Keep your calendar in sync across all your devices Private by default - No ads, no trackers, and no data harvesting - We can’t spy on your calendar or misuse your data - Protected by the same end-to-end encryption used in Proton Mail - Event names, descriptions, and participants are stored with zero-access encryption - Based in Switzerland, all your data is protected by strict Swiss privacy laws People before profits - Funded by users, not advertisers — Privacy is our business model - Built by scientists and engineers who met at CERN and MIT and founded Proton Mail - Used by high-profile journalists and organizations globally What others say about Proton: “Proton has now made it stupid-easy to encrypt your schedule. Information about what you plan to do, where, and with whom, can be just as sensitive as the messages you send and receive.” Gizmodo Follow Proton on social media for all the latest news and offers: Facebook: /proton Twitter/X: @protonprivacy Reddit: /protonmail Instagram: /protonprivacy EULA: http://www.apple.com/legal/itunes/appstore/dev/stdeula

About

Pi Epsilon

A decentralized, anonymous, and end-to-end encrypted communication platform offering voice, text, video, and group calls. It provides robust security features and full user control over the server environment, bypassing third-party providers.

Highlights
  • Decentralized and anonymous communication
  • End-to-end encryption
  • Voice, text, and video calls
  • Group video conferencing
  • User-controlled server hosting
  • Decoy obfuscation tools
Features
Read full description

The Pi Epsilon (Π Ε) Communication Platform is a cutting edge decentralized, anonymous, end-to-end encrypted communication platform that includes voice, text, video, chat, and group video conference calls through a proprietary configuration that bypasses the usage of any third-party provider platforms. The Π Ε communication platform can reside on a dedicated obfuscated Virtual Private Server (VPS) or anywhere, resident to the customer’s location. The Π Ε Communication Platform offers one of the most protective cyber design decoy obfuscation tools from any nefarious attacker looking to obtain information of the real Π Ε communication platform. Look no further for your secure communication needs. Advantages • Decentralized, anonymous, real-time communication, end to end encryption protocol. • Customer has full control and oversite of the communication platform server. • Π Ε can reside on a dedicated Virtual Private Server, private rack server, or a physical server resident within the customer location. • No dependencies of any third-party provider and or backbone infrastructure. • Π Ε resides on a virtual dissimulated encrypted server (VDES), as a decoy obfuscation tool environment, shielding the real IP from any nefarious inquiries. • Π Ε includes voice, text, video, chat, and group video conference. • Supports the federate infrastructure, where multiple instances of Π Ε servers can communicate with each other. • Customer retains Admin console control to manage users, permissions, and resources.

Screenshots

Proton Calendar4 screens
Pi Epsilon4 screens

Verdict

The call

The clearest difference is rating: Pi Epsilon at 5.0 against Proton Calendar's 4.0. Pi Epsilon also leads on in-app purchases (none vs 2). Proton Calendar's advantage is ratings volume (1.4K vs 4) and update cadence (every 5 weeks vs every 6 months). On price, ads, monetization model and device support there is nothing between them.

Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS

CostPrice · In-app purchases · Ads · Monetization

Both are free to download. Proton Calendar sells 2 one-off in-app purchases. Pi Epsilon asks for nothing beyond the download.

ReceptionRating · Positive reviews · Number of ratings

Pi Epsilon holds the better App Store score, 5.0 against 4.0. That said, the two scores are not equally well evidenced: Proton Calendar has 1.4K ratings behind it against 4, so its average is the more settled of the two.

UpkeepUpdate frequency

Proton Calendar ships an update every 5 weeks, Pi Epsilon every 6 months. The most recent releases landed on September 22, 2026 and September 17, 2026 respectively.

Scorecard4 real differences · 6 level
Proton Calendar versus Pi Epsilon: the parameters behind the verdict, then further details
ParameterProton CalendarPi Epsilon
PriceFreeFree
Rating4.0 (1.4K ratings)5.0 (4 ratings) — better
Positive reviews41.2% of reviews
Number of ratings1.4K — better4
Update frequencyEvery 5 weeks — betterEvery 6 months
AdsNoNo
In-app purchasesYesNo — better
MonetizationFreeFree
DevicesiPhone, iPadiPhone, iPad, iPod — better
Requires iOS16.015.0 — better
Further details — not scored
Size185 MB147 MB
Age rating4+4+
DeveloperProton AGChesapeake International Consulting, LLC

Customer experience

Proton Calendar

All ratings1,415 ratings
Positive71.1%
Neutral13.7%
Negative15.2%
Written reviews626 reviews
Positive41.2%
Neutral25.7%
Negative33.1%

Pi Epsilon

All ratings4 ratings
Positive100.0%
Neutral0.0%
Negative0.0%

Bugs and requests

Proton Calendar

Reported bugs

3 issues
  • Issues with time zone settings
  • Notifications not working reliably
  • Inability to edit shared events

Requested features

5 requests
  • Widgets for quick access
  • Ability to invite and share calendars with others
  • Support for importing/exporting calendar data
  • Customization options (colors, alerts, etc.)
  • iPad-optimized version

Pi Epsilon

Not enough reviews yet to summarise bugs or requests.

In-app purchases

2 purchases

Proton Calendar

One-time2
  • Mail Plus (1 year)$59.99
  • Proton Unlimited$149.99
None

Pi Epsilon

No in-app purchases

Questions

Is Proton Calendar free?
Proton Calendar is free to download, with in-app purchases available.
Is Pi Epsilon free?
Pi Epsilon is free to download, with no in-app purchases.
Which has better reviews, Proton Calendar or Pi Epsilon?
Pi Epsilon is rated higher. Proton Calendar averages 4.0 out of 5 from 1.4K ratings, while Pi Epsilon averages 5.0 from 4 ratings.
Do Proton Calendar or Pi Epsilon have ads?
Neither Proton Calendar nor Pi Epsilon shows ads.
Which is updated more often, Proton Calendar or Pi Epsilon?
Proton Calendar ships an update every 5 weeks, and Pi Epsilon every 6 months. Most recently, Proton Calendar was updated on September 22, 2026 and Pi Epsilon on September 17, 2026.

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