automaticDark is a Firefox extension that can switch to dark theme automatically on a schedule
Firefox has a really cool native dark theme. You're probably aware of this, but in case you don't know, you can switch to it from the add-ons page: select the themes option on the side bar and click on the Dark theme.
This process has to be done manually every time you want to switch between themes. Windows 10 has a night mode that can be enabled automatically, and when this option's enabled, Firefox will enable the dark theme on its own, and reverts to the default theme when the operating system turns off night mode.
But not everyone uses Windows 10. If you're on a different operating system, and want your browser to switch to a dark mode on a schedule, you can use an add-on called automaticDark. You may also find the add-on useful if you want to enable and disable the dark theme on a custom schedule.
The extension doesn't have a toolbar icon which means that you need to head to the add-ons page to manage it. The options page lets you set the dark theme at sunset, and switches back to the daytime theme at sunrise. The default options for sunrise and sunset are set to 8:00 AM and 8:00 PM. You can change the time manually, like I've done. That's a pretty useful option to have, since not everyone works during the same hours of the day. There is an option to automatically set the sunrise/sunset time, but if you enable it, you'll be prompted to grant the geo-location permission for the add-on.
There are two more options on the page: these allow you to set the daytime theme and the nighttime theme. You can choose from any of the three default themes that Firefox ships with: Default, Light and Dark. If you're a night shift worker and prefer using the day theme during the night (and vice versa), you can switch them per your requirement.
Once you have set the sunset and sunrise times, automaticDark will enable the corresponding theme automatically. I've been using it for about a week, and it has worked flawlessly. The extension does not change the appearance of websites, i.e., it will not change a page's background to a dark color. If you want that, you should try Dark Reader.
Custom themes support
I don't like the built-in themes in Firefox, so I use third-party themes. Will automaticDark work with it? Absolutely, as long as the theme that you're using is listed in the Add-ons > themes section (and not under Extensions), it should work. The easiest way to check this is right from automaticDark's options page, just click the daytime or nighttime theme setting, and the third party theme that you want to use should be available in the drop-down menu. Set it as the theme, and you are good to go.
On the other hand, I found that extensions which change the appearance of the browser like NightOwl, Firefox Color aren't supported. This isn't automaticDark's fault, it's just that these add-ons use a different method (modified CSS) to change the look of the browser.
automaticDark is an open source extension. The full name of the extension is automaticDark - Time-Based Theme Changer. This is a useful add-on, even for those on Windows 10.Advertisement