My point is this: Most people don't know about UTC/TAI/UT1 or any other standard. They know what's common knowledge, and what's common knowledge is that one day is 24 hours precisely, one hour is sixty minutes precisely, and one minute is sixty seconds precisely. Therefore, when writing software to interface with most people, including businesses with contracts defined in terms of those time definitions, one day is 24 hours or else you end up with problems.