Date inputs when editing an issue should use localised date format
The date format used in Redmine is selectable in the administrator settings.
When not using the default format of 'yyyy-mm-dd', places where dates are rendered read-only, the date is output in the selected localised format, however when actually editing issues, the date fields (e.g. start date) don't use the localised format, they still use 'yyyy-mm-dd'.
From a user perspective this is a little inconsistent and confusing. At least for numeric date formats, it would make sense to adjust the input format according to the selected local alternative.