HSQL

Historical Structured Query Language

A query language for temporal databases. An extension of SQL. The query may contain IN INTERVAL, which limits searches to a time specific interval, FROMTIME ... TOTIME which prefaces a query with a time interval, and CONTAINS which limits INTERVALS to a specific point in time. There are also built-In temporal functions: CURRENT( ), which returns the current tuples of a relation, HISTORY( ) which returns the historical tuples of a relation, ELAPSEDYEARS( ) which returns the number of years between two arguments, and ELAPSEDMONTHS( ) which returns the number of months between two arguments.

N. L. Sarda, "HSQL: A Historical Query Language"