Temporal Extensions in the SQL Standard
Both ANSI and ISO published a revision of the SQL standard in 2011, referred to as SQL:2011 . An important new feature of SQL:2011 is the ability to create and manipulate tables whose rows are associated with one or more temporal period definitions.
The first attempt at extending the SQL standard for temporal data support was made in 1995. A set of proposals incorporating the language extensions based on (but not identical to) TSQL2  was submitted to both ANSI and ANSI SQL committees for consideration. However, this effort was abandoned in 2001 because of various reasons. A new attempt at standardizing temporal extensions with a different set of constructs was made in 2008. These language extensions are now part of SQL:2011.
Valid time, the time period during which some information is regarded as correctly reflecting the...