Every time I read this story the part that always surprises me again is the units command. Converting from 3 millilightseconds to miles is brilliant, and I am delighted every time that the units command can do this.
<https://news.ycombinator.com/item?id=36988917>
<https://news.ycombinator.com/item?id=36995046>
And Trey Harris's "500 mile email" story is what clued me on to GNU units and its capabilities.
Reminder: if you're on MacOS, or one of the BSDs, your default units is from BSD, not the GNU version, and is far less capable. GNU units can be installed on MacOS through Homebrew. The package is "gnu-units", the command is "gunits" once installed.
Edit: Corrected Homebrew package name.
brew install gnu-units
(I run the command far more often than I install the package.)
(I've not touched MS Windows in a couple of decades now.)
EDIT: #19 here https://www.ibiblio.org/harris/500milemail-faq.html
It's also entirely plausible that a local definitions file was used to provide the unit that didn't come in the default install. Hence the anachronism is merely "potential" instead of "definite"