The "Denmark - English (en_DK)" locale presents the date in a weird/unexpected form. The expected form is YYYY-mm-dd but KDE forces is (for unknown reasons) to this rather unexpected style dd/mm/YYYY. STEPS TO REPRODUCE 0. install locales for en_DK.UTF-8 1. Open Formats system settings module 2. select "Denmark - English (en_DK)" for the "Time" 3. check the output under examples 4. compare it with the output of LC_TIME=en_DK.UTF-8 date +"%x %X" OBSERVED RESULT Time format is "dd/mm/YYYY" like 10/12/2018 EXPECTED RESULT Time format is "YYYY-mm-dd" like 2018-12-10 SOFTWARE/OS VERSIONS See what is shipped in Debian stretch (or Debian buster on 2018-12-10)
Locale handling is done by the Qt frameworks. If this is reproducible with Qt 5.11 or newer, please report this issue to Qt developers via https://bugreports.qt.io/
Please note that en_DK is not an offical (ISO supported) locale, but a hack for the limited POSIX locale system. Qt does not use the POSIX database, but the CLDR database.