This is the sort of thing which encourages people who exult science to act as if those who don't are stupid. Where is the word "sidereal" in the headline? Leaving it out is part and parcel of scientism's self assertion as the one true belief.

That's not what people ordinarily mean by "day" - the boxes on a calendar are all the same size. It's not even what people ordinarily mean by "shortest day" - i.e. the day with the least amount of daylight.

Not only is it a fact of little or no practical utility, it is nearly impossible to verify by reasonable means and therefore for the vast majority of those who assert it to be true it is a revelatory truth accepted on faith. Only those with full notebooks, big telescopes and accurate chronometers have a chance of verifying the hypothesis. Otherwise, it is just part of a canon.