Is this still a bug or has it been resolved? BUG-disallowed Social Security numbers Machine's regional settings of the date/time are not honored when working with map services published to ArcGIS server 10.6.1. Identify using the REST API that contains a date field, it comes back formatted as MM/DD/YYYY.
From what I can see on my end, this defect has yet to be resolved. It was logged for ArcGIS Server 10.6.1. Is this where you are seeing the behavior or have you noticed it in a more recent version?