Date display format
- This article applies to both Thunderbird and the Mozilla Suite.
By default the Mozilla Suite and Thunderbird display the time only (without the date) for messages with today's date. For messages older than this, they display both the date and time. You can change the information that is displayed by modifying preferences.
The date format and the time format are set in your computer's operating system. You can change these formats by configuring your computer's settings.
Changing the information displayed
To change the information displayed, modify these preferences. If you are using the configuration editor and the preference that you want to modify is missing, create it as an Integer preference:
|Preference||Applies to||Default value|
|mail.ui.display.dateformat.today||Messages with today's date||0|
|mail.ui.display.dateformat.thisweek||Messages with a date in the past seven days||2|
These preferences can have the following values:
|Value||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|
* Some operating systems have only one date format. On these systems, the values 1 and 2 produce the same result.
Example: For example, you want to to set the format for messages that have today's date so that both the date and the time are displayed, and you choose to do this by editing edit a user.js file. You add this line to the file:
Alternatively, you can set the preference using about:config or the Thunderbird Config Editor.
Configuring the date/time system settings on your computer
In addition to the settings shown above, the precise display formats for date/time can also be affected by the system settings for date/time on your computer. For instance, depending on your computer's system settings, the numerical display format for the date could be "31.12.1999", "1999/12/31", "12/31/1999", or something else.
In Windows XP, you can change the settings for date/time format by going to the Control Panel. See here for detailed instructions.
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 only for showing dates, set the "LC_TIME" environment variable (for example, "LC_TIME=en_GB"). If you want the ISO 8601 date format (YYYY-MM-DD), use the "en_DK" locale.
Note: there is a bug in Thunderbird where LC_ALL overrides the setting of LC_TIME. If you have old applications which require LC_ALL to be set to "C", then you might find that merely setting LC_TIME is not enough to change the date format.
In order to set this value only for Thunderbird you can either use a separate script to invoke Thunderbird that contains the following lines:
#!/bin/sh export LC_TIME=en_DK # or whatever you want [ "$LC_ALL" != "$LC_TIME" ] && unset LC_ALL # only necessary if set to something different from LC_TIME exec <FullPathToYourOriginalThunderbirdCommand>/thunderbird "$@"
make this shell script executable and place it in a directory that is in your binary search path *before* the original Thunderbird command.
OR, if you are using thunderbird 2.0, you can create a special script that thunderbird will load on startup. This can either be created as a system change by creating this file in your thunderbird/init.d directory where thunderbird is installed, OR a personal change by creating an init.d directory in your .thunderbird directory in your home directory.
mkdir -p ~/.thunderbird/init.d
Create a file named S00Locale.sh in the init.d with the contents
make sure it's set executable
chmod +x S00Locale.sh
If you get an error message saying that "LC_TIME is not an identifier", you need to declare it before exporting it. Change the script to read:
LC_TIME=en_DK export LC_TIME
If you are on an system using the utf8 charset (like Kubuntu/Ubuntu) and get this errromessage:
(thunderbird-bin:4587): Gtk-WARNING **: Locale not supported by C library. Using the fallback 'C' locale.
you need to add .utf8 (or .UTF-8) to the LC_TIME export, like export LC_TIME=en_DK.utf8.
You could also see a list of all the available locales using the locale -a command:
$ locale -a C en_AU.utf8 en_BW.utf8
In Mac OS X, go to the "International" panel in System Preferences. The date format can be adjusted under the "Format" tab.
By default, the standard mail format is used for the "Date:" heading when printing a message. While this is not configurable within Thunderbird itself, the printing tools extension can be used to set the date format to the same format that Thunderbird uses when displaying the message. The format used in headers/footers of the printed page is the same format and defaults to your system's short date definition. 
- ConfigDate extension for Thunderbird: allows you to configure the date display format without needing to manually edit the user.js file.
- ConfigDate extension for SeaMonkey: allows you to configure the date display format without needing to manually edit the user.js file.
- International ISO-8601 Date Format on Thunderbird for the problem and fix for UTF-8 systems