CG: If you are looking for a “practical” consequence lehalacha from this difference, consider the 18 minutes it takes unworked dough to become chametz. This is defined by chazal in maseches pesachim to be 1/40 of 12 hours or 1/80 of a full day. However, due to the changing length of the day, dough would become chametz on our clocks at about half a millisecond before the 18 minutes are up. You can see why I put the word practical in quotes!
Thanks for this amazing over-my-head discussion! I did a little research as you suggested in one of your posts and found that although the earths rotation is on average slowing down and extending a “24-hour day”, there are days that are faster than 24 hours including July 1 2018.
Therefore, how could one know exactly how long on any given Pesach day what 1/40 of 12 hours or 1/80 of a full day would measure?