Wrong date and time formats

Steps to reproduce

1. Set your system and browser to language=German and locale=Germany
2. Open the Calendar app with Firefox desktop
3. Create a new event

Expected behavior

Date shows DD-MM-YYYY and time in 24h format

Actual behavior

Date shows MM-DD-YYYY and time in 12h format

Calendar app version

7.x

Additional info

With https://github.com/nextcloud/calendar/pull/6423 we replaced the custom (and buggy) datepicker with a native one. The objectives were usability and accessibility. Most platforms come with a very capable date and time picker. Firefox only has a date picker, which was considered an acceptable trade-off, because keyboard input is always possible.

This is an upstream issue with Firefox. I'm filing the ticket here for transparency and to have a central point for updates/discussion.

Relevant Firefox ticket(s):

• Poor support for datetime-local (no time, and null-value if time not selected) https://bugzilla.mozilla.org/show_bug.cgi?id=1850383

You can also test the datetime picker at https://developer.mozilla.org/en-US/docs/Web/HTML/Element/input/datetime-local. It works well with Chrome but not with Firefox. The problem does not appear to be specific to Firefox.

Reproduce the German-locale event creation flow in Firefox desktop and compare it with Chrome using the linked datetime-local test page. Read Firefox ticket 1850383 and the discussion around pull request 6423; the issue identifies an upstream limitation, so no repository change or local completion condition is specified.