Steps to Reproduce

1. Switch JIRA default language to portuguese
2. Create a new sprint in a project
3. Start the sprint with the start date and end date
4. Edit the dates by click a date from the pop-up calendar

Expected Results

Date are set correctly

Actual Results

Invalid date format error is shown

Workaround

If manual changes the initial letter of the month from capital letter to lowercase works (see attachments)