Cannot enter project start date in GH, date format invalid

When trying to set a start date for a version in GH (planning board or chart board), following error is thrown:

Invalid format: "25.08.2010" is malformed at ".08.2010"

See also screenshot: error-after-setting-startdate-in-gh.png

Date/time configuration is changed to match DE/AT standards. I have attached screenshot from Jira Admin area and the jira.property file (datetime-config-in-jiraui-and-property-file.png)