Setting Due Date with German Language results in portal requests failed to be created.

Summary

Creating a "Due Date" hidden field for a Request Type in a Service Desk project while the system language being "German" will lead to customers unable to create requests via the portal. The customer will hit into the "This form contains a hidden field that does not have a valid default value configured" error.

Steps to Reproduce

1. Go to General Configuration
2. Change Indexing Language to German
3. Change Default Language to Deutsch (Deutschland)
4. Change Default user time zone to Europe and Timezone to (GMT+01:00) Berlin
5. Go to the Service Desk project > Request Type > set "Due Date" as a hidden field
6. Change the date picker field (e. g Due Date) to any date in December (e.g 4/Dez/32 10:00 PM)

Expected Results

• JIRA should be able to recognize "Dez" abbreviation for December
   

Actual Results

 
Note
If the same hidden field is viewed from a English profile in the instance it will show the following:

It will look correct in one language profile and show an error in another, the same goes for the Customer Portal, depending on which language:

• If the system is set to German, the date will be set to 2/Dez/29, the English profile customers will not be able to create tickets. Because Jira is expecting the input to be 2/Dec/29
• If the language profile is switched to English and the due date is set to 2/Dec/29, the German profile customers will not be able to create tickets. Because Jira is expecting the input to be 2/Dez/29

Workaround 1

Change the due date to a month which is both acceptable in English and German, such as 4/Nov/20, the value "Nov" is accepted in both languages.

Workaround 2:

From within JIRA, change the date format from 02/Dez/29 to 02.12.29.

1. Navigate to General Configurations > click on "Advanced Settings":

Update your settings so that they match what is shown below:

1. jira.date.picker.javascript.format=%d.%m.%y
2. jira.date.time.picker.javascript.format=%d.%m.%y %H:%M
3. jira.date.time.picker.java.format=d.MM.yy H:mm
4. jira.date.picker.java.format=d.MM.yy