How to Fix Tuta Calendar Timezone Issues in Hardened Firefox

Preface

For my scheduling needs I’ve been using Tuta Calendar (Tutanota) since I de‑Googled. It was bumpy at first — slow sync and connection issues — but the Tuta team has since ironed out the bugs. Ever since I hardened my Android, I use their email and calendar app on my phone and the web-client at app.tuta.com on the desktop.

Most of my scheduling is done on mobile, but recently I noticed an iCal calendar subscription (Better F1 Calendar) showed the wrong race times in the browser while displaying correctly in the phone app. I tracked down the cause of the time zone glitch—it was my hardened browser security settings that hid my time zone (using default UTC).

This is a quick post on how to fix time zone display problems with websites when using a hardened Firefox (I’m using Floorp these days, but it applies for all Firefox forks).

Bypass Browser Fingerprinting Protection

Important

To prevent the wrong display of time zone, we have to turn off the “faking” of time zone details. This is a security trade-off—only proceed if you’re okay with websites knowing your real location.

1. If you’re okay with time zone leaks to all the sites you visit, you can apply this rule in the about:config page:

   privacy.resistFingerprinting.testing.setTZtoUTC — set to false

2. If you want to exclude just Tuta from resistFingerprinting protection:

   privacy.resistFingerprinting.exemptedDomains — add app.tuta.com (comma separated, I would not recommend * wildcard e.g. *.tuta.com, to be on the safe side).

3. Restart browser and check if the time zones of your calendars are showing the correct times.

4. If it’s not working, try deleting the cookies of the problematic site (be it Tuta, Proton, or other calendar web UI).

About Browser Hardening

I have always used strict security rules in my browser, so much so that I find myself with broken websites more often than not! Ever since the Firefox fiascos¹, I have been using hardened Firefox forks on both macOS and Android. My browser and plugin recommendations are:

• Android

  • IronFox
  • Cromite (if you prefer a Chromium fork)

• macOS

  • LibreWolf
  • Floorp
  • Zen

• Plugins

  • uBlock Origin
  • Decentraleyes

• DNS

  • Quad9 - I set the DNS on the OS level and turn off “DNS over HTTPS” in the browser so it doesn’t override my Quad9 settings. (Use https://on.quad9.net to check if you’ve set it up correctly.)

Further Reading

Here are some sites I think are useful for learning about hardening browser security and improving privacy.

• Browser Hardening: An Entry-Level Guide to Protect Digital Privacy
• Firefox Hardening Guide
• Resist Fingerprinting
• Cover Your Tracks

Summary

Both of these settings are more narrow/specific and doesn’t require you to turn off global fingerprinting protection completely (which I do not recommend). By excluding Tuta or turning off just the time zone protection, events will now display correctly without disabling global fingerprinting protection.

If you want to try Tuta out for their privacy-focused services, consider using my affiliate link for one additional month free for their yearly membership, thanks!