I am running my self-hosted version of Vikunja, have been for a while.
I noticed when I enter a date in the task name, Vikunja helpfully sets that as the due date, however, it’s incorrectly interpreting the date in US format.
For example, today I typed in “12/6” and it set it to 6th of December, instead of 12th of June.
Both default and user timezone is set correctly to “Australia/Brisbane”, language set to English.
I can’t find any configurable setting for locale, region, date format, etc.