JIRA Popups still using english formats (see screenshot)

i would summarize it like this:

1. have a language setting for the JIRA installation (default english)
2. make your personal profile another language
3. the popup which appears for the calendar is still in english, that means its returning the english format
4. the validation is on the main page (e.g. german profile setting)

I would guess that the popup is not translated and it is even hardcoded that it takes the english format or it takes the general configuration, like you said. As you can see on the screenshot it says today, which is not german like the rest of the browser.