A long time nuisance with the Thunderbird email client is that the time display on the calendar is shown in a 24-hour time format. This article shows how to change that.

For example: 3:20PM shows on the calendar as 15:20. Converting all the times on the calendar in my head gets a little old. Note in the following screenshot that the dates after noon are all in 24 hour time (e.g. 15:00 is the same as 3:00PM).

Before Changing Time

My annoyance level finally reached the point that I did a little research. Here is how to change the display.

Steps

  1. Launch Thunderbird and go into Settings. Click the gear icon at the bottom of the left sidebar or select the Hamburger menu in the upper right and pick “Settings”
  2. Select the “General” settings option
  3. Scroll to the very bottom of the general settings page and click the “Config Editor…” button to open the Advanced Preferences.
  4. Search for “intl.date_time.pattern_override.time_short”. If it is not there, add it as a string. (See the sample screen shot below)
  5. Edit the value to be h:mma and click the checkbox to accept the change.
  6. Exit and restart Thunderbird.

Settings

Once we’ve made the change and return to the calendar, the times show up like this. 3:00PM is now a little more intuitive.

After Changing Time Setting

Here is a link to the Mozilla Support page that pointed me in the right direction.

Customize Date and Time formats in Thunderbird

And this is a link to an overkill page that documents all the time and date format strings.

Unicode Reference Page