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changing date formats in thunderbird

UPDATE 2022

date and time format override preferences using Thunderbird Config Editor

feature available starting from Thunderbird 91
date and time format override preferences will allow to apply date and time formats which are different and independent of those defined by the regional localizations in your operating system or Thunderbird. You need to create these preferences and set them to your preferred format.

=> set 
intl.date_time.pattern_override.date_short        yyyy-MM-dd        2025-12-31    Short date
intl.date_time.pattern_override.time_short        HH:mm             09:59         Short time

≡ > Preferences > General > Config Editor > click “show al” buttom
create a preference called intl.date_time.pattern_override.date_short
(weird procedure : )
search for intl.date_time.pattern_override.date_short
it will return empty
then change type to “string”
click on the plus sign
value = HH:mm (which stands for short date)
save
exit  Config Editor & restart thunderbird

==> #TODO ; gedaan maar het werkt niet, uitzoeken.
blijkbaar “als bedoeld”

added intl.date_time.pattern_override.date_short with value yyyy-MM-dd and, in effect, the date/time column changed (after restart) to the format yyyy-MM-dd, hh:mm

add-on ~~ConfigDate~~

add-on allows to change the date format in the headers colums ( sent / received)
doesn’t work anymore since TB 78

thunderbird display.dateformat

http://kb.mozillazine.org/Date_display_format

format wanted : yyyy-mm-dd = date +%F in bash
for me, time is irrelavnt for personal mails , could be looked up in rare cases when nedded

Open [[thunderbird-config#advances preferences]] and change the default value for these settings :
| setting | meaning | default | modified |
| ----------------------------------- | ------------------------------------------- |:-------:|:--------:|
| mail.ui.display.dateformat.today | Messages with today’s date | 1 | 3 |
| mail.ui.display.dateformat.thisweek | Messages with a date in the past seven days | 2 | 3 |
| mail.ui.display.dateformat.default | Older messages | 2 | 3 |

value meaning example
0 No date , time only 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

values 1 & 2 : in linux, these settings are based on your locale.
If the environment variable “LANG” is set to “en_US”, for example, Thunderbird will show the date in “MM/DD/YYYY” format.
To override the locale, but only for showing dates, set the “LC_TIME” environment variable (for example, “LC_TIME=en_GB”).
use the locale command

==If you want the ISO 8601 date format (YYYY-MM-DD), use the “en_DK” locale==.
update : 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.

thunderbird “received” date handling

http://blog.dmitryleskov.com/small-hacks/putting-the-received-column-in-thunderbird-to-work/ :
Each mail header has a “Date” , i..e date and time of the message sent.
In real life that is oftentimes an incorrect timestamp.
(reasons : system clock malfunction , incorrect timezone setting, deliberate forging by spammers, etc)
Therefore many email clients sort messages by time received at final destination, extracted from the Received: header.
However, inThunderbird the received column displays the same timestamp as “Date”, thus useless.
The default folder view therfore shows only the Date column.

To change this functionality :
Open [[thunderbird-config#advances preferences]]

  • Locate the mailnews.customDBHeaders preference, e.g. by typing “dbh” in the Filter field.
  • Double click it, or select and press Enter.
  • If the preference was not set : type “Received” and click OK.
  • If some extension has already populated the preference, add “ Received” to the end of the list of headers, separating it with space.

  • Close the Config Editor and restart Thunderbird.


    From now on, the newly received messages should have a proper value in the Received column.

If you want the old messages have also, you need to tell Thunderbird to re-download the headers and rebuild the index for each IMAP folder.
To do that, right-click the folder you want to refresh, select Properties from the pop-up menu, and click the Repair Folder button.

An option under “Tools > Options, Advanced, General” allows to select whether date/time display will follow
- the application locale (adjusted by operating system’s format settings for that locale)
- or the locale selected in the operating system’s regional settings.

In other words, an US English Thunderbird can use, for example, German formats.