I got this system running in a constructed world, but it actually makes sense there - unlike in real life. It’s something like this:

>space settlers leaving Earth colonise another planet
>seconds are still useful for their scientific paraphernalia, so they keep the unit
>days in the new planet are not 86.4ks long, so they ditch “Earth day” as a measuring unit
>since ditching Earth days, might as well ditch minutes and hours. 1ks (~15min) is good enough of a measuring unit
>human life gets extinct from Earth but survives in the other planet
>millenniums go on, and the descendants of those settlers in the new planet send new settlers into other planets
>one of the colonies hit Earth, without realising that it was humankind’s birthplace
>colony capsule is fucked up - the cryogenic chambers are intact so the settlers survive, but every other system gets wrecked
>you got a bunch of people from a scientific civilisation thrown in the middle of the jungle, without access to the tech that they’re used to
>they use some primitive methods (like a dripping bucket) to determine the length of the day in Earth, around 80ks
>since it’s really inaccurate might as well use a round number. 80ks per day it is
>split the day in eights so you can get “neat” 10ks divisions
>split those divisions into 100s
>their descendants eventually go full roaming tribal, but keep the measurement units inherited from their starfaring ancestors