Undated SF

Science fiction can become dated but remain worth reading, e.g., The Time Machine and The War Of The Worlds. It is good when a science fiction writer sometimes gets part of the future right. Heinlein had mobile phones, water beds and waldos. The last are named from Heinlein's novel.

Skillful sf writers can also avoid writing texts that date too quickly. Although Poul Anderson wrote his Time Patrol series from 1955 to 1995, he carefully avoided describing the near future. Gorbachev is mentioned in a novel dated 1991 but no political leader of the 1990's had been named before then. In the opening story, an instructor at the Time Patrol Academy in the Oligocene demonstrates:

"...the gadgets in a typical room. They were the sort you would have expected by, say, A.D. 2000: unobtrusive furniture readily adjusted to a perfect fit, refresher cabinets, screens which could draw on a huge library of recorded sight and sound for entertainment. Nothing too advanced, as yet."
-Poul Anderson, Time Patrol (New York, 2006), p. 8.

Indeed. This group of cadets has been recruited from 1850-2000. Some of them will already be familiar with these domestic gadgets. The others can be introduced to them. Whitcomb from 1947 and Everard from 1954 will have less difficulty than their colleagues from the 1850's. One girl with "...iridescent, close-fitting culottes...green lipstick...fantastically waved yellow hair..." (p. 6) sounds familiar from later in the century. Is she "...the girl from 1972...a rising young physicist in her own period..." (p. 9) who speaks up later?

In Anderson's "Delenda Est" (1955), Piet Van Sarawak is from Venus whereas, in SM Stirling's "A Slip in Time" (2014), he is from a terraformed Venus, not contradicting but completing Anderson. In a timeline without the terraforming, the acidic Venerian environment would boil lead.