How to change Thunderbird's display time to 24h format?

Currently Thunderbird displays time in AM/PM mode.

How can I change it to 24h mode?

UPDATE 1:

$ locale |grep LC_TIME
LC_TIME="en_US.UTF-8"

Solution 1:

Ok, solved it:

1) Make sure you have the locale you need, can't say which you specifically need but when you know you create it like this (using en_DK.utf8)

sudo locale-gen en_DK.utf8

2) To make sure this locale is in effect for thunderbird you add it to the script that starts thunderbird, so first find that script:

2a) find the right script

which thunderbird

In my case: /usr/bin/thunderbird

2b) add locale to the script (I use the editor geany):

gksudo geany /usr/bin/thunderbird

Add this in the beginning of the script (I just put at the very beginning):

LC_ALL="en_DK.utf8"
export LC_ALL

Just want to add this:

https://help.ubuntu.com/community/Locale

EDIT: as pointed out by pl1nk A better solution would be to NOT touch the /usr/bin/thunderbird script and instead create the script '/usr/local/bin/thunderbird' with this content

#!/bin/sh
LC_ALL="en_DK.utf8"
export LC_ALL
/usr/bin/thunderbird $@

make sure it's executable

sudo chmod a+x /usr/local/bin/thunderbird

Then check if it's being used to start thunderbird:

which thunderbird

should respond with this:

/usr/local/bin/thunderbird

Now thunderbird can be started as before.

Solution 2:

There's a Super Date Format thunderbird addon: