I would like to raise an important feature request regarding Proton Calendar, which would allow me to leave the Google ecosystem entirely.

Context: I have already migrated my email and most of my usage to Proton, yet I still keep a Gmail account solely to maintain my Google Calendar. This forces me to keep a live Google account, which goes against my privacy goals.

What I need to close my Gmail account:

1. True two-way synchronization with external calendars (especially Google Calendar). Currently, subscribing to an external calendar seems read-only. I need the ability to edit imported events and have those changes reflected back to the source calendar — full bidirectional sync.

2. An open protocol or API (e.g., CalDAV) so third-party applications can read from and write to Proton Calendar. I want my other apps (booking tools, productivity apps, third-party clients) to fetch data from my Proton Calendar and also insert events into it. Without interoperability, Proton Calendar remains locked inside the Proton ecosystem, whereas a calendar's core value lies in interfacing with the rest of my tools.

3. A complete and straightforward migration path from Google Calendar: events, shared calendars, reminders, and attachments.

I am confident many users share this situation: we want to cut ties with Google entirely, but the calendar is the last lock holding us in. Robust two-way sync plus CalDAV/API access would be decisive — making Proton a full replacement for Google, not a partial one.