1. A method of responding to queries sent to temporal relational databases, the method comprising: receiving, by a computer system, a query at a temporal relational database including at least one temporal element specifying a first instant in time for reconstituting the database and a second instant in time from which to extract data from the database, wherein data changes and schema changes in the database are associated with a temporal history indicating times at which the data changes and schema changes are factually valid; reconstituting, by the computer system, the database responsive to the at least one temporal element based on: filtering out from a plurality of transactions stored in the database data changes and schema changes in the temporal history that are factually valid at times later than the first instant in time to select transactions with a transaction time later than the first instant in time; ordering the selected transactions by sequence time, transaction time, and valid time to create linear ordered pan temporal timelines; and including data changes and schema changes in the temporal history that are simultaneously factually valid at times earlier than or concurrent with the first instant in time based on an intersection in valid time of the linear ordered pan temporal timelines at the second instant in time; extracting, by the computer system, data responsive to the query from the reconstituted temporal relational database; and sending, by the computer system, the extracted data in response to the query.