Just seen the section under 'Data as Products' -> '03 Ports and Consistency' -> '03 More on consistency' which introduces Datomic as one potential solution to make temporal queries easier. If you were going to go down this route you might also consider CRUX which is another Clojure based solution but with even more explicit support for bi-temporality.
It might be going to be discussed in a later section, but up to now the presenter has often pushed dealing with these broader concerns into the 'platform'. Is this another example? If the legacy systems are architected with application data that doesn't typically support temporality but are able to emit the latest state as that state or some entity as that entity changes then I guess the platform could provide a capability based on 'something' like a datomic / crux db to provide a aggregate data product to support a temporal consistent view downstream ?