You can read about the whole sordid mess, but it turns out that’s a surprisingly complex question. In the end, the new component ended up with no less than three distinct options for calculating the difference between two time periods.
Anyway, this leads me to a bizarre conversation that was detailed by Joe Veix on Death And Taxes: “Two body builders argue on the internet about how many days are in the week“. The whole exchange is hilarious and is well worth spending some time with.
Still, it did remind me uncomfortably of the week where I nearly went insane trying to figure out how to minus one date from another date. Rabbit holes can be dangerous.