I would like to globally set the Linux date format to ISO, which looks roughly like this:

2009-03-16 15:20:00

With varying levels of detail, such as omitting time, seconds, etc.

I know that for some applications, you can configure this manually, but I'd like it to be automatically set for every program.

I'm specifically using Ubuntu Intrepid, but a general solution that would work across all distributions would be best.

6 Answers 6


Set your locale date environment variable LC_TIME to "en_DK" Set it in your .bashrc or similar, or check man locale for how to set it system-wide.

On ArchLinux all of the Locale settings are in /etc/rc.conf and customisations are set up in /etc/rc.local

# Local multi-user startup script
export LC_TIME="en_DK"
  • 2
    I found that nowadays (Ubuntu 12.04) you need to set it to "en_DK.UTF8", but otherwise, great to know that Danish folks use sane ISO date format ;-).
    – pfalcon
    Aug 24, 2013 at 19:22
  • 4
    @pfalcon it is not "english in Denmark" as the abbreviations would make one believe, it is mock, which name is a joke that is lost to me... see the references from this freebsd bug, which unfortunately decided not to adopt it: freebsd.org/cgi/query-pr.cgi?pr=137870 that said, it may be very well that in Denmark everyone uses the ISO date formate tho.
    – gcb
    Feb 12, 2014 at 8:28
  • @gcb: So should we use en_DK or not?
    – einpoklum
    Mar 22, 2017 at 14:29
  • 4
    @einpoklum It's a workaround for English speaking countries, There is no ISO format for weekday names. The discussion on this bug for glibc is quite informative (You have to read past Ulrich Drepper being angry): sourceware.org/bugzilla/show_bug.cgi?id=4628
    – Sekenre
    Mar 27, 2017 at 10:20
  • If en_DK is no good, try en_SE if your system has it. You should append .UTF-8 to the value if your existing locale has that suffix in the output of the locale command.
    – Walf
    Aug 11, 2020 at 7:21

It's explained at length in this guide: http://ccollins.wordpress.com/2009/01/06/how-to-change-date-formats-on-ubuntu/

  • I went and found the link since prestiginate said he couldn't post hyperlinks. And I actually had been there before, but I guess I never bothered doing it on this machine, making me think whatever I tried before didn't work.
    – Neil
    Jun 1, 2009 at 21:18
  • If anyone wants the Unicode string for ISO dates, it's <U002b><U0025><U0059><U002d><U0025><U004d><U002d><U0025><U0064>. The python line that makes this is: ''.join(['<U00{}>'.format(hex(b)[-2:]) for b in '+%Y-%M-%d'.encode('UTF-8')]) Dec 16, 2017 at 17:18

Open locale.conf with your editor

# $EDITOR /etc/locale.conf

and insert the line


after saving the file run

# locale-gen
# env-update && source /etc/profile

and test the result

# ls -al /home
drwxr-xr-x   8 root             root      4096 2011-12-2  .

Some people would advise to change your local to german "en_DK" this kind of works if you don't mind the day and month names being in german. Since I cannot post hyperlinks,and this board sees my linux commands as hyperlinks.... (nice one)... I can only say you search (google) how-to-change-date-formats-on-ubuntu and click the first link.

  • 1
    He meant this link: ccollins.wordpress.com/2009/01/06/…
    – Neil
    Jun 1, 2009 at 21:16
  • 4
    en_DK is not the German locale either, it's danish.
    – GodEater
    Jun 2, 2009 at 7:08
  • 2
    it is neither. "en" is English. the "DK" part is the country which sets things like currency symbols, date formats and decimal separators, etc. The first part is the language, which would determine month names.
    – gcb
    Feb 12, 2014 at 8:30

I wish this were generally possible, but POSIX locale categories have only so many formats, most of which correspond to more historic formats/scenarios, but if you get d_fmt and t_fmt right, things seem to improve generally. Some time ago, I’ve created one that comes as suitably close to a full ISO 8601 locale as possible on a Debian GNU/Linux (glibc) system.

The way to do this correctly is not entirely trivial. You’ve got to create a full locale of your own, even if you only use it for LC_CTIME. You’ve got to edit some values manually, but only for date/time; you can, thankfully, just include the defaults for the others.

I’ve done this for de_DE (or rather de_DE.UTF-8) as base locale. The resulting locale definition file looks as follows (but read on below):

comment_char %
escape_char /

% $MirOS: contrib/hosted/tg/deb/de_DE@iso8601,v 1.1 2021/04/05 21:13:47 tg Exp $
% This is an alternative locale definition file, GNU libc compatible,
% which provides an LC_TIME category that is mostly conformant to DIN
% 5008 and ISO 8601. It uses %-d as an extension (use the alternative
% date_fmt if not supported); the timezone offset is rendered without
% colon due to https://bugs.debian.org/799476 which is not proper but
% the best we can currently do; date +'%Y-%m-%dT%H:%M:%S%:z' works.
% Install with:
% $ sudo localedef -i de_DE@iso8601 -f UTF-8 -c de_DE.UTF-8@iso8601

% glibc
title     "German locale for Germany with DIN ISO 8601 date/time format"
source    "BOSng"
contact   "mirabilos"
language  "German"
territory "Germany"
revision  "1.0"
date      "2021-04-04"

category "i18n:2012";LC_IDENTIFICATION
category "i18n:2012";LC_CTYPE
category "i18n:2012";LC_COLLATE
category "i18n:2012";LC_TIME
category "i18n:2012";LC_NUMERIC
category "i18n:2012";LC_MONETARY
category "i18n:2012";LC_MESSAGES
category "i18n:2012";LC_PAPER
category "i18n:2012";LC_NAME
category "i18n:2012";LC_ADDRESS
category "i18n:2012";LC_TELEPHONE
category "i18n:2012";LC_MEASUREMENT

copy "de_DE"

copy "de_DE"

abday         "So";"Mo";"Di";"Mi";"Do";"Fr";"Sa"
day           "Sonntag";/
abmon         "Jan.";/
mon           "Januar";/
% this *should* be the first line; GNU cannot even do its own extensions right
%d_t_fmt      "%Y-%m-%dT%H:%M:%S%:z (%Z), %G-W%V-%u (%a)"
d_t_fmt       "%Y-%m-%dT%H:%M:%S%z (%Z), %G-W%V-%u (%a)"
d_fmt         "%Y-%m-%d"
t_fmt         "%H:%M:%S"
am_pm         "";""
t_fmt_ampm    ""
week          7;19971130;4
first_weekday 2
first_workday 2
cal_direction 1
% use the second line if %-d does not work for you
date_fmt      "%A, %-d. %B %Y, %H:%M:%S %Z"
%date_fmt     "%a %Y-%m-%d, %H:%M:%S %Z"

copy "de_DE"

copy "de_DE"

copy "de_DE"

% glibc
copy "de_DE"

% glibc
copy "de_DE"

% glibc
copy "de_DE"

% glibc
copy "de_DE"

% glibc
copy "de_DE"

If you wish to do this for some other locale, such as es_ES, you’ll need to make the following modifications to it (in my example, I’m unashamedly copying from glibc localedata/locales/es_ES):

  • change title, language and territory in the head (and the others, source, contact, revision and date as well while there) to suitable values (e.g. language Spanish, territory Spain)
  • if not using glibc, you might need to remove a few entries commented with % glibc (such as LC_NAME), but don’t if your system does support them (the -c flag to localedef should also make it accept that, but YMMV)
  • change all the copy "de_DE" lines (there’s a lot of them!) to copy "es_ES"
  • change abday to a list of weekday name abbreviations (starting with Sunday), e.g. "dom";"lun";"mar";"mi<U00E9>";"jue";"vie";"s<U00E1>b" (here you have also the chance to use 2‑letter or 3‑letter abbreviations to suit your taste)
  • change day to a list of full weekday names, e.g. "domingo";"lunes";"martes";"mi<U00E9>rcoles";"jueves";"viernes";"s<U00E1>bado"
  • change abmon and mon to abbreviated and full month names ("ene";"feb";… and "enero";"febrero";…)
  • save as es_ES@iso8601
  • change the comment near the beginning appropriately, the compile command is now sudo localedef -i es_ES@iso8601 -f UTF-8 -c es_ES.UTF-8@iso8601

Then, you can export LC_TIME=es_ES.UTF-8@iso8601 to use this. Alternatively, if you do not have superuser priviliegues, you can use LOCPATH (or MUSL_LOCPATH) to install the locale data locally; for glibc, this looks as follows:

mkdir -p ~/.local/locpath
localedef -i es_ES@iso8601 -f UTF-8 -c ~/.local/locpath/es_ES.UTF-8@iso8601

Thereafter, export LOCPATH=$HOME/.local/locpath and LC_TIME=es_ES.UTF-8@iso8601 to use.

For other languages, countries, encodings, etc. proceed correspondingly.

In theory, you can also set LC_ALL to it, since it copies the remaining locale category definitions from the corresponding master file for the chosen locale.


Probably the best way to do this, but not break things is to follow the walkthrough at


  • 3
    Whilst this may theoretically answer the question, it would be preferable to include the essential parts of the answer here, and provide the link for reference.
    – Jenny D
    Dec 29, 2017 at 20:19

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