But then, also, the concept of time is arbitrary.

Our time is based on the rotation of the earth and its orbit around the sun -- periods upon which most if not all earth creatures have their natural rhythms and cycles synched. Hardly an arbitrary concept ;-)

Although you're correct in that we *could* arbitrarily recognize a 30-hour day if we didn't mind 14am sometimes being the dead of night and sometimes being the height of daylight; or Joctebuary (we'd have to re-jigger weeks and months and years, too) sometimes being winter-cold or summer-hot ...

A lot of trouble to go through just to get some extra free "time," but at least the Liberals would be happy ;-)