Overview

Proton Calendar handles recurring events, invitations, and notifications on mobile devices or desktop browsers. End-to-end or zero-knowledge encryption protects event titles, descriptions, locations, and invited people, making it a strong fit when the contents of appointments are sensitive. Proton is incorporated and headquartered in Switzerland and follows Swiss privacy laws.

Mail integration lets users send invitations and add events directly from Proton Mail. Calendar sync is one-way, a meaningful limitation for people who need changes to move in both directions between services.

Key features

Appointment scheduling automatically updates availability and adds confirmed meetings, reducing manual upkeep for people arranging appointments. Scheduling links and video meeting support extend the service beyond a basic personal calendar, while event management covers creating, editing, deleting, and managing recurring events and invitations.

Paid users can share calendars by link with other calendar services on the web, and can import and export calendars. These options improve coordination and portability, but they are not part of the free plan. Notifications arrive through desktop browsers or mobile devices.

Pricing

The Free plan is free and includes essential Proton Calendar features with up to 3 calendars. It is a practical starting point for individuals who can work within that cap and do not need paid sharing or calendar import and export.

Mail Plus and Unlimited each allow up to 25 calendars for 1 user, but their prices are custom pricing. Paid Proton Mail plans also include additional calendar features, including sharing by link; the extra calendar capacity suits users managing several calendars, though the single-user seat count does not make either plan a multi-user purchase.

Subscriptions purchased through proton.me renew automatically. Users can switch plans at any time, and upgrades receive prorated credit.

Platforms

Proton Calendar has apps for Android and iOS, with notifications also supported through desktop browsers. Its calendar sync is one-way, so it is less suitable for users who rely on bidirectional updates across calendars.

Who it's for

Choose Proton Calendar if protecting event details matters more than broad platform coverage, or if Proton Mail is already part of your workflow. The free plan works for a small personal setup; paid plans better suit a single user who needs more calendars, link sharing, or import and export. Look elsewhere if you need more than one paid-plan seat or two-way sync.

Pros and cons

Pro: Encryption protects titles, descriptions, locations, and invited people, which is valuable for private appointments.
Pro: Appointment scheduling, scheduling links, and video meeting support make it useful for arranging meetings as well as keeping a personal calendar.
Con: The free plan stops at 3 calendars and excludes sharing by link and import and export, limiting collaboration and portability without paying.
Con: One-way sync and paid plans limited to 1 user each may frustrate people coordinating across multiple services or with a team.

Alternatives

Browse calendar apps for more options by category. Lark is worth considering if you want a freemium option with a Starter plan for 20 users, 100 GB storage, 18 months of message history, and 1,000 automations per month. Microsoft Outlook Calendar is another freemium choice, with a one-month free trial for Microsoft 365 Personal, Family, and Premium.

Calendar.com offers a free plan for individuals and a Standard plan starting at 20.00 USD per month; consider it if those plan terms suit your needs. Teamup has a free tier with 5 sub-calendars, 5 users, 1 custom field, and 1 year of historical data, making it a fit for users who need those shared-calendar limits. Cozi is a family-oriented alternative with a shared calendar, automatic notifications, shared grocery and to-do lists, and a recipe library in its free plan.

TimeTree may suit people who want shared calendars with comments and photos. TimeFinder is another freemium calendar option. Notion Calendar is free and supports connecting multiple calendars.

Verdict

Proton Calendar is a strong choice for privacy-conscious individuals, especially those already using Proton Mail: encrypted event details and practical scheduling tools are its clearest advantages. Its three-calendar free cap, paid-only sharing and portability, one-way sync, and single-user paid plans make it a weaker fit for larger teams or people who need calendars to stay synchronized in both directions.

	Merkuro Calendar (formerly Kalendar)	Proton Calendar
Free plan	Yes	Yes
Free trial	No
Paid from	Free	Free
Platforms	Linux, Windows	Android, iOS
Free plan	Yes	Yes
Shared calendars		Yes
Scheduling links		Yes
Calendar sync		one_way
Mobile apps		ios and android
Video meeting support		Yes

Merkuro Calendar (formerly Kalendar) vs Proton Calendar

Merkuro Calendar (formerly Kalendar)

Proton Calendar