This is a simple Firefox WebExtension that allows you to automatically switch between your themes based on the current time.
Set Firefox to change the UI to a dark theme during the night and change back to a light theme during the day!
Try the extension at https://addons.mozilla.org/firefox/addon/automatic-dark/
privacy.resistFingerprinting
flag in about:config set to True
, the extension will not be able to detect your timezone (#5). You would need to make an adjustment in your settings to compensate for this.
Feedback and pull requests welcome! What do you think? Let me know!