Err, we created the "seconds in a day" metric, by picking the time span of seconds.
The earth's rotation takes a constant K time. Whether the time is 86400000 seconds or 50 seconds or 642552 seconds, is based on whatever arbitrary value we pick to mean "a second".
The earth's rotation takes a constant K time. Whether the time is 86400000 seconds or 50 seconds or 642552 seconds, is based on whatever arbitrary value we pick to mean "a second".