Issue Summary

In Jira Data Center, when inputting a value into a field that's using a MM/dd/yy format, it allows users to put incorrect values into it.
This issue is reproducible on Jira Data Center 8.20.6 and 9.12.0 so far.

Steps to Reproduce

1. Navigate to Jira Administration > General Configuration > Advanced Settings
2. Set jira.date.picker.java.format to MM/dd/yy
3. Set jira.date.time.picker.java.format to MM/dd/yy h:mm a
4. Navigate to a field that uses a date picker (Target Start or Target End)
5. Input 01/20/12023 or 11/29/233 into the field.
6. Run a REST API call against the issue like so to see the value set:

https://serverName/jira/rest/api/2/issue/issue-Key?fields=customfield_<id of date field> 

Expected Results

Error should be returned in the UI showing that this is invalid input and the REST response shouldn't have the incorrect value.

Actual Results

The UI will take the incorrect input and may display it correctly or incorrectly depending on the value that's inputed.
For example, if we input 11/29/233 we see that it sets the date to 29/Nov/33 in the UI and 0233-11-29 with in REST response:

Workaround

Using the default d/MMM/yy doesn't seem to allow for incorrect input.