Steps to Reproduce:

1. Create a New Project.
2. Create a New Issue.
3. On the Due date specify date like

   10/VI/15

4. Press ENTER.

Expected Result:
The Due Date will be set to 10 June 2015

Actual Results:
There will be an error appear saying to input in the correct format like

 duedate: You did not enter a valid date. Please enter the date in the format "d/MMM/yy", eg. "8/Dec/14" 

Notes:

• There is a possibility that java SimpleDateFormat could not handle such input as it is expected it as a String Type rather than Numerals.
• This will affect the countries that is using Roman Numerals on their date.
• Using the Czech Translation Pack for JIRA 6.2.5 will able to make it work
• After investigation, this is issue is a JDK 1.8-specific problem. Using JDK 1.7 would be able to use Roman Numerals in the date picker.

Workaround:
Change the instance JAVA to use JDK 1.7. If it is using built-in JAVA (Installer Bundled), follow the documetation below:

• https://confluence.atlassian.com/display/JIRA/How+to+Use+System+JRE+Instead+of+Embedded+JRE