Serververwaltung > Item Fields > Creating Fields > Setting Field Editability > Key Considerations
  
Key Considerations
Editability rules are evaluated on the Windchill RV&S client’s time zone.
Editability does not apply for fields ID, Created Date, Created By, Modified Date, Modified By, and Type. It also does not apply for phase, range, item backed picklist, query backed relationship, and computed fields.
Editability rules cannot include a computed expression that requires an external information function.