A shame indeed, they were only a few decades too early! The support for "Time Varying Data" gets discussed briefly in this 1995 paper by Stonebraker "The Design

A shame indeed, they were only a few decades too early! The support for "Time Varying Data" gets discussed briefly in this 1995 paper by Stonebraker "The Design of Postgres" > POSTQUEL allows users to save and query historical data and versions. By default, data in a relation is never deleted or updated. Conventional retrievals always access the current tuples in the relation. Historical data can be accessed by indicating the desired time when defining a tuple variable. > [...] Finally, POSTGRES provides support for versions. A version can be created from a relation or a snapshot. Updates to a version do not modify the underlying relation and updates to the underlying relation will be visible through the version unless the value has been modified in the version. https://dsf.berkeley.edu/papers/ERL-M85-95.pdf https://dsf.berkeley.edu/papers/ERL-M85-95.pdf