While developing a certain part of thepid.de I needed to input datetime into a form. Luckily html got you covered with datetime-local as type attribute for an input field, which works well. However I was pretty annoyed that the format of the datetime input in my browser was the American AM/PM format.

My computer language is set to English, but locale for Date, Currency, etc.. is set to German. This is done by setting the correspondingLC_ variables. Turns out firefox does not care about that.

After some kagiing I found a solution: Go to about:config and switch intl.regional_prefs.use_os_locales to true.

Thanks Zibi Braniecki.

Now it looks so good.