Windows English installation set up for Dutch system.
HA language English: am/pm times.
HA language Dutch: 24h times.
iPhone English installation set up for Dutch system.
HA language English: 24h.
2 years later and there is still no sense…
EDIT:
I can’t believe it, it was actually fixed in 0.109 or 0.110. Open your profile and set language to English (GB).
EDIT 2:
The unbelieve was true. It is not fixed. Logbook is 24h now and some other elements too, but clicking on stuff in the UI still shows am/pm. History also lots of am/pm.
EDIT 3:
Home Assistant rollercoaster life, as always… In Firefox set English (United Kingdom) as language. I guess just wipe out United States anywhere you see it and take regular English or UK English.