CorrectICS

Google Workspace to Proton Mail Calendar Migration

Many people moving from Google Workspace to Proton Mail are doing it for privacy, simplicity, or a broader provider switch.

The calendar part of that move usually depends on one file: the exported .ics.

If that file is clean, the migration is manageable. If it is old, oversized, or messy, the import can break in ways that are hard to trust.

If you already have a failing import, start with /fix.

1. Typical migration flow

A normal Google Workspace to Proton Mail calendar migration looks like this:

  1. Export your calendar from Google Workspace / Google Calendar.
  2. Save the .ics file.
  3. Open Proton Mail Calendar.
  4. Import the calendar file.
  5. Verify that important events, recurring meetings, and timezones came across correctly.

That flow is most reliable when the source calendar is relatively clean.

2. Where migrations get messy

Problems are more likely when the calendar:

  • contains many years of event history
  • has complex recurring events
  • has been moved between systems before
  • includes timezone-sensitive appointments
  • was imported and re-imported multiple times in the past

In those cases, the export is not just a transfer file. It is a historical record with a lot of room for weirdness.

3. Common problems after importing into Proton Mail

Duplicate events

Repeated imports or confusing old event identifiers can create duplicate-looking results.

See: ICS Import Created Duplicate Events – How to Clean It Up.

Recurring series do not look right

Migrated recurring events may appear incomplete, expand differently, or behave inconsistently.

Wrong times

Timezone definitions are a common issue whenever calendars move across providers.

See: Fix ICS Timezone Errors (Events at the Wrong Time).

Import rejection or partial import

If Proton Mail seems to accept the file but results look incomplete, or if it rejects the file outright, the ICS itself likely needs inspection.

See: ICS File Won’t Import? Fix Google Calendar and Outlook Errors.

4. Best practice: import once, then verify

A simple habit prevents a lot of cleanup pain:

  • keep the original export untouched
  • import once
  • verify the results before trying again

Check:

  • a few recent events
  • a few older events
  • recurring meetings
  • all-day events
  • timezone-sensitive appointments

If you see clear problems, stop there. Repeated retries can make it much harder to tell what came from the original file and what came from multiple imports.

5. When to repair the ICS file first

Repair first if:

  • the file is unusually large
  • the calendar carries decades of history
  • you already see duplicates or wrong times
  • the import fails or behaves unpredictably

The broader pattern is covered here: Why calendar imports break after migration.

CorrectICS helps by giving you a validation step before you commit to another import attempt.

Start here: /fix.

6. Migration checklist

Before calling the move finished:

  • export from the correct Google Workspace calendar
  • keep a backup of the source .ics
  • import into Proton Mail once
  • verify event counts and spot-check key events
  • validate and repair the file if anything looks off

If you want a concrete example of how ugly a migration artifact can get, read: How We Repaired a 30-Year Google Workspace Calendar for Migration to Fastmail.

7. Next step

If the migration is breaking, do not keep guessing.

Fix your .ics file in seconds

Upload an iCalendar file and get a clean, import-ready version for Google Calendar, Outlook, Apple Calendar, and Teams.

Try the CorrectICS Autofix Tool Back to Help