Missed due date shown in wrong language

Hey folks,

I don't know if this is a bug or a feature. I couldn't find another issue report on this, also searched on nextcloud-l10n and in the pull requests.

Describe the bug

• Nextcloud language is set to "English (US)"
• Nextcloud locale is set to "German"
• when I look at the card I've set a due date to, it shows "vor N Stunden"
• when I change the locale (not the language) to "English", the message is in English ("N hours ago")
• when I change the locale (not the language) to "French", the message is in French ("il y a N heures")

So it seems that the due date message is coupled to the locale instead of the language.
It makes sense to couple the calculation to the "locale"-setting, but the actual message should be in the set "language".

To Reproduce
Steps to reproduce the behavior:

1. Go to Settings > Language and set it to "English (US)"
2. Go to Settings > Locale and set it to "German"
3. Go to Deck
4. Create a new card with a due date in the past
5. Look at the message "vor N Stunden" on the card

Expected behavior
I expected this to show the message in the language I set (English (US)) instead of the locale I set.

Client details:

• OS: Arch Linux
• Browser Firefox Developer
• Version 83.0
• Device: Notebook

Please let me know if this is intended behavior or something we actually want to fix.

Thank you & greetings
Michael

No source file or test is named. Reproduce the issue in Deck with English (US) as the language and German as the locale, then trace the due-date message's language and locale handling. Done means the date calculation still follows the locale while the displayed message follows the selected language.