en_DK locale uses dot as clock separator

The "Denmark - English (en_DK)" locale presents clock in a weird/unexpected form. Most locales use ":" as separator but en_DK uses "." for unknown reason.

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 separator is "." like in "11.19.03" or "11.19"

EXPECTED RESULT
Time separator is ":" as in the libc locale. Like "11:19:03" or "11:19"

SOFTWARE/OS VERSIONS
See what is shipped in Debian stretch (or Debian buster on 2018-12-10)

See https://bugs.kde.org/show_bug.cgi?id=401948