The field name 'date' in EventUpdate shadowed the 'date' type from datetime, causing Pydantic v2 to interpret Optional[date] as Optional[None] — rejecting all non-null values with a 422 error. Fix: rename import to 'date as _date' and use '_date' in all annotations. Also improve error handling in admin forms to properly display 422 validation error messages. Co-Authored-By: Claude <noreply@anthropic.com>