1930, 1950, 1990, 2000

The present moment is always the point of transition between past and future, thus also between real past history and fictional future histories. The twentieth century has been a period of fundamental changes and of successive waves of future historical writing. 

Equally significant in any future history are:

(i) if it is a single novel (Wells, Stapledon), its date of publication - if it is a series (Heinlein, Anderson etc), the date of publication of its earliest published instalment;

(ii) the earliest date in its fictional chronology. 

(i) tells us what was "future" to the author. 

(ii) tells us an earliest date at which the fictional timeline has definitely diverged from our "real"/experienced timeline, albeit with the additional complication that sometimes instalment are written later but set earlier. Thus, in Poul Anderson's Psychotechnic History, "Un-Man" ceased to be the earliest instalment when "Marius" was published and, in Anderson's Technic History, "Wings of Victory" ceased to be the earliest instalment when "The Saturn Game" was published.

Olaf Stapledon's Last And First Men (1930) begins by referring to the "European War." 

HG Wells' The Shape Of Things To Come (1933), BOOK THE FIRST, TO-DAY AND TO-MORROW: THE AGE OF FRUSTRATION DAWNS, includes a section on "The Great War of 1914-18."

The first instalment in Robert Heinlein's Future History, "Life-Line" (August, 1939) (the month before the outbreak of World War II), is set in 1951.

The first date and event in Poul Anderson's "History of the Future" (1955) is "1950 Korean War." Between 1950 and 1980 comes World War III.

Jerry Pournelle's CoDominium Chronology begins with Neil Armstrong on the Moon in 1969 and the CoDominium itself is created in 1990.

Larry Niven's Known Space future history begins with interplanetary exploration, 1975-2000.

Poul Anderson's Technic History begins by quoting a report dated 2057. This is in "The Saturn Game," published in 1981.

Thus, we read these seven future histories in conjunction with the history of the twentieth century.