7.0.X, 7.1.X, Master
STEPS TO REPRODUCE
1. Create a new site
2. Configure the site to have German as default language.
3. Create a new page called Form.
4. Add the Form portlet to the page.
5. Go to the Content -> Forms portlet for the site and create a form with just a date field.
6. Configure the Form portlet to display the form with date field.
7. To make sure that German locale is applied, add "de" to the URL
8. Click on the date field and select a date.
Should see a date with periods separating day from month from year. E.g., 22.11.2018
We see a date with slashes like this: 22/11/2018