How did Julius von Ficker distinguish actum from datum in historical documents?

In the field of diplomatics, the German scholar Julius von Ficker made a significant contribution by distinguishing between the actum and the datum of a document.1

He defined this distinction as the difference between the verbal legal procedure itself and the subsequent formal documentation of that event. Specifically:1

• Actum: Refers to the date or circumstances of the actual legal enactment or performance of the transaction.21
• Datum: Refers to the date or circumstances of the issue of the document that records the previously performed legal act.21

Understanding this differentiation is essential for historians, as the date inscribed on a charter may reflect either the moment the agreement was reached or the later time when the written record was officially produced. This insight remains a fundamental principle for determining the provenance and authenticity of historical records.2