There's an old saying "two is an impossible number". In programming, we either deal with one of a thing, or a collection of things. The cases where there are exactly two things are uncommon (cue HN coming up with a bunch of exceptions). In the case of points in time, even bi-temporal leaves out a third, implicit point: now.
Fascinating. While 2 is indeed a rare quantity/cardinality, "2-ness" is a ubiquitous quality of digital systems.
By human choice, though. We could be using N different thresholds of electrical charge or current, but instead we define ranges as "0-enough" and "1-enough".
The irony being of course that there are two scenarios.