<p>How do I change the system-wide short date format in Ubuntu?  For example, Thunderbird is showing dates in the DD/MM/YY format, and I would like to change it to MM/DD/YY or YYYY-MM-DD.</p>

<p>The best information I can find so far is in this thread:</p>

<p><a href="http://ubuntuforums.org/showthread.php?t=193916" rel="noreferrer">http://ubuntuforums.org/showthread.php?t=193916</a></p>

<p>Edit: I want to change the system-wide date format, so that all my applications use this new date format.</p>

Thunderbird uses the system's date format, and that format depends on the system's locale settings. You have two options:
modify the system locale, the instructions are in the forum thread you linked above, or
set
```
LC_TIME
```
to a locale that uses the format you want. The
article
linked by
Craig H
suggests
```
en_DK
```
.