I think we should have a scientific definition of time -- something that is highly static and precise (such as the time it takes for an atom to vibrant a number of times, or the time it takes light in a vacuum to travel a certain distance) and a cultural definition of time that is more loose than UTC (There is always the same number of seconds in a day, but maybe some days have shorter seconds than other days).

Cultural time is fine and dandy for human level stuff. Keep that simple. Scientific time for business, engineering and scientific stuff.