future history. However, this involves extending the same science fictional imagination in the opposite temporal direction. Further, the Time Patrol presents an implicit future history, giving many hints about future periods. See The Time Patrol Timeline.
Poul Anderson wrote:
more future histories than any other sf author;
a time travel series, the Time Patrol, to which nothing else is comparable.
Like Heinlein's Future History and Anderson's own Psychotechnic History, the Time Patrol series can be appropriately collected in two dense volumes. See here. In fact, it has been although I slightly disagree with the order in which the installments are presented.