I have ubuntu 10.04 running Thunderbird 14.0

How do I change the date format to international standard? (eg; 2012-07-26)

My system date already shows this format.

7 Answers 7


How to get YYYY-MM-DD HH:MM date format in Thunderbird 60

sudo ln -s /usr/share/i18n/locales/en_DK /usr/share/i18n/locales/root
echo 'root.UTF-8 UTF-8' | sudo tee -a /etc/locale.gen
sudo locale-gen
LC_TIME=root.UTF-8 thunderbird

Why LC_TIME=en_DK.UTF-8 thunderbird no longer gives this date format

Thunderbird and Firefox now use CLDR (Unicode Common Locale Data Repository), which does not have the ISO 8601 date format in en_DK.


  • 1
    This is the only up-to-date answer to this problem I found on SE. Contains all the references to the upstream bugzilla tickets as well. I read them all and the workaround given here is indeed the most appropriate one. In fact, you can even set LC_TIME=root.UTF-8 in your /etc/locale.conf to have it affect the entire system and without having to specify the modified locale env var whenever you start thunderbird (from whatever location).
    – FichteFoll
    Jan 3, 2020 at 5:04
  • 1
    As an update, I recommend using LC_TIME=lt_LT.UTF-8 because the root locale in CLDR has Sunday as the first weekday, while lt_LT has Monday as the first weekday and does not use localized names for months (at least in TB's calendar view).
    – FichteFoll
    Jan 3, 2020 at 17:10

I know of 4 ways to alter TB's date. Take your pick ;) (you just need 1)

  • Quick Locale Switcher add-on for TB. Might be the easiest one.

  • Mozilla's official documentation in changing date formats.

    In Thunderbird, choose Tools –> Options –> Advanced –> General > Config Editor




    V   Meaning                                 Example date and time
    0   No date                                 10:23 AM
    1   Your system's long* date format         Friday, December 31 2003 10:23 AM
    2   Your system's short* date format        12/31/1999 10:23 AM
    3   Year and month, separated by a slash    1999/12 10:23 AM
    4   Abbreviated day name                    Fri 10:23 AM 
  • Change the startup command to

    export LC_TIME=en_GB.UTF-8 && thunderbird %u

    (Dash Main Menu > Internet > Thunderbird > Properties) Ofcourse change en_GB.UTF-8 to what you need

  • Change your custom locale (/usr/share/i18n/locales) as explained on ubuntuforums.org.

  • 3
    Outdated. In 2019, Thunderbird no longer has any option with "dateformat" in its name.
    – Joachim W
    Sep 10, 2019 at 8:00
  • @JoachimW it's not outdated. You just create those ints and reboot Thunderbird.
    – Det
    Apr 11, 2020 at 8:57
  • Hm. None of the mentioned datetime formats is particularly useful in general. Either part of the date is missing or the order of day month year is wrong, or it is too long a format for display next to the subject of e-mails. Aug 11, 2021 at 16:09

Does depend on what you want to achieve - in Ubuntu 12.04 I got stuck with US locale settings (mm/dd/yyyy), wanted to switch to UK (dd/mm/yyyy), and couldn't find any tips.

Then I stumbled on system settings-> language support -> regional formats tab, change to English (United Kingdom). Easy!

Hope this helps someone


Unfortunately those answers don't show you how to set the date to YYYY-MM-DD format.

If you follow these instructions, setting the LC_TIME variable to en_DK.utf8 (I'd advise putting it in a script that calls Thunderbird) it will show YYYY-MM-DD HH:MM in the message view and give you the option of using YYYY-MM-DD in the calendar as the 'short' format.


  • I put "LC_TIME=en_DK.utf8 " at the beginning of the command value in my Thunderbird menu shortcut. May 27, 2014 at 0:11

Since Thunderbird 60.0 you need to set LC_TIME as stated in the other answers but you now also need to change the "Date and Time Formatting" option in the advanced preferences in the "General" tab.


The fastest, very reliable and solid way to change the date, is to download the Super Date Format addon.

Go to Menu > Add-ons, then in Add-ons manager select the Extensions tab and search for Super Date Format add-on on (on the upper right).

When you download and install it, go to Super Date Format preferences (Display > Date Format) and customize the format.

You are going to have a format like this:

/%Y-/%m-/%e   %H:%M %p

In which:

  • /%Y is the full year
  • /%m is the month
  • /%e is the number day

It may seem difficult but the whole configuration is super-easy when you open the configuration tab, because it explains everything you need to know.


This works on Ubuntu 16.04 LTS and the Thunderbird 54.* but is not limited to this version only.

It also works on Ubuntu 18.04 LTS with Thunderbird v52.9.1. There may be warnings that the extension is not compatible but you can ignore them.

  • Finally a working approach. Note: you have to activate it, too: Display > Date Format Preferences > Enable on Date/Received column Jun 20, 2017 at 16:46
  • 1
    In 2019, I cannot find this addon. What I could find is an addon called 'Enhanced Date Formatter'.
    – Joachim W
    Sep 10, 2019 at 8:03
  • 1
    @JoachimW You are right. The Super Date Format is now outdated and being replaced by the Enhanced Date Format , which also works like charm. Sep 13, 2019 at 21:12

How to get YYYY-MM-DD HH:MM date format in Thunderbird 78.7.1

sudo locale-gen lt_LT.UTF-8
sudo update-locale

LC_TIME=lt_LT.UTF-8 thunderbird


  • Of all the answers listed here, this is the only one that works for me (ubuntu 20.04, thunderbird 78.14). I believe that the other answers either refer to older versions of thunderbird, or make assumptions about the environment/locales which are not true for my machine.
    – erik
    Dec 31, 2021 at 20:46

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.