Valid Time and System Time

Valid time describes when a fact applies in the modeled business world. System time describes when a version is recorded as current in a specified database or system. A customer may move on March 14 while the database records that move on March 20. Name the system and the timestamp semantics rather than treating every timestamp as event time.

A bitemporal model retains both validity intervals and system-version intervals. It can distinguish what a March 16 report could have known then from a later correction of March 16. A loaded_at column on a row that is overwritten does not preserve prior system versions. Reproducing a report also needs its query and other inputs.

Database system versioning is not automatically business-valid history. SQL Server temporal tables track database versions using their documented transaction-time behavior; business validity needs its own design. Source recording time may also precede arrival in a feature store. For predictive features, test availability in the system that actually served the prediction.

Reference: Microsoft temporal tables. See Data Modeling for Operational and Analytical Systems for the worked example.