Query of the Study Update DateTime (0008,041F) Key Attribute using date and time range matching allows an SCU to identify changes that have occurred since a prior inventory was obtained. This enables incremental processing of updates to synchronize the SCU's data to that held by the SCP, and is crucial to the migration use case. It may also support important quality assurance and other processes. In order to maintain backward compatibility with existing repository databases, this Attribute is identified as optional, but its importance to a number of use cases and its potential for significant performance improvement makes implementation highly desirable.