- By default, the dates are shown with US locale
It's possible to change the Thunderbird UI to f.e. German: Edit > Preferences > Language > English|French|German|Italian
If the English is used and german date formating is wished, check: https://support.mozilla.org/en-US/kb/customize-date-time-formats-thunderbird
In config editor (Edit > Preferences > Search: config > Config Editor) set:
intl.date_time.pattern_override.date_short - dd.MM.yyyy
intl.date_time.pattern_override.time_short - HH:mm
