Issue Summary

The error "Invalid format" is shown in the atlassian-jira.log when building and releasing versions.

This is reproducible on Data Center: yes

Steps to Reproduce

1. In JIRA Admin > System > Look and Feel set the Day/Month/Year Format to a format using spaces, e.g. 'dd.MMM.yy' (or any other date time format that is not the default)
2. Go to the Versions list of any projects, and click Release for a Version; You will see it released without problems
3. Then click Unrelease for the same version
4. Now click Build and Release, and the screen refreshes multiple times falling into a loop.
5. Return to the Versions lists and you will see the Version still is unreleased

Expected Results

The Version should be released regardless of the format configured in Look and Feel

Actual Results

The Version remains Unreleased and the Version page enters into a loop.

The below example exception is thrown in the atlassian-jira.log file:

http-nio-8080-exec-XXX url: /jira/rest/bamboo/1.0/status/10002/SCRUM-SP-X; user: USER ERROR USER XXXXX SESSIONID IP_ORIG /rest/bamboo/1.0/status/10002/SCRUM-SP-5 [c.a.j.p.e.bamboo.service.BambooReleaseServiceImpl] Unexpected Error Has Occured Performing Release
java.lang.IllegalArgumentException: Invalid format: "14.Jun.23" is malformed at ".Jun.23"
	at org.joda.time.format.DateTimeFormatter.parseLocalDateTime(DateTimeFormatter.java:900)
	at com.atlassian.jira.datetime.JodaDateTimeFormatter.parse(JodaDateTimeFormatter.java:42)
	at com.atlassian.jira.datetime.DateTimeDatePickerFormatter.parse(DateTimeDatePickerFormatter.java:28)
	at com.atlassian.jira.datetime.DateTimeFormatterImpl.parse(DateTimeFormatterImpl.java:51)
	at com.atlassian.jira.util.DateFieldFormatImpl.parseDatePicker(DateFieldFormatImpl.java:42)
	at jdk.internal.reflect.GeneratedMethodAccessor1139.invoke(Unknown Source)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.base/java.lang.reflect.Method.invoke(Method.java:566)

Workaround

1. Go to JIRA Admin > System > Look and Feel
2. Revert the Day/Month/Year Format to the default format settings: dd/MMM/yy

Or, release the version manually from the project's administration page for version.

Notes

There seem to be correlation with the Jira Admin > System > General Configuration > Advanced Settings > jira.date.picker.java.format. If reverting the values in 'Look and Feel' doesn't work, check the jira.date.picker.java.format value and sync it with the value in 'Look and Feel'