Hello @roy lee ,
EmployeeHireDate is an AzureAD attribute. It is present at AADConnect cloud connector schema.
These attributes aren't present in an Active Directory Domain Services (ADDS) schema.
Here's the article which lists the available attributes in ADDS,
https://learn.microsoft.com/en-us/windows/win32/adschema/attributes-all
I will work with an engineering team to get the document updated to avoid confusion.
Hope this helps.
Let us know if this answer was helpful to you or if you need additional assistance. If it was helpful, please remember to accept it and complete the quality survey so that others in the community with similar questions can more easily find a rated solution.