Future History Chronologies

In Ensign Flandry by Poul Anderson, the Terran Empire is over four hundred years old. (1) According to Sandra Miesel's "Chronology of Technic Civilisation," the Empire was founded about 2700 and Ensign Flandry is set in 3019, only about three hundred and nineteen years later. (2) However, Anderson's texts warrant no chronological precision. When the Chronology was being compiled, an editorial decision decreed that Dominic Flandry was born in 3000. Since Ensign Flandry does clearly state that its title character is nineteen, the date of 3019 for the novel automatically followed. (3)

The Foundation Trilogy by Isaac Asimov and Earthman, Come Home by James Blish are set in remote futures with no dates given. When, later, precise dates were specified, the effect was to shorten the histories implied by the earlier narratives. The Time Chart of Larry Niven's Known Space future history states that the dates as given in one story must be seen as erroneous. Robert Heinlein's Methuselah's Children and Time Enough For Love disagree about Lazarus Long's age. However, I do not accept Time Enough For Love as a valid addition to Heinlein's Future History.

Some generalisations emerge from these observations:

future histories usually are not pre-planned;
when a work has been published, its author becomes another reader with a fallible memory;
authors imagine longer periods when writing narratives than when compiling chronologies.

(1) Anderson, Poul, Ensign Flandry, London, 1976, p. 104.
(2) Miesel, Sandra, "Chronology of Technic Civilisation" IN Anderson, Poul, The Rise of the Terran Empire, Riverdale, NY, 2009, pp. 477-478.
(3) Ensign Flandry, p. 32.