Originally Posted by jib71

Wikipedia states that there's a 30-hour clock convention that's used in written communications by business whose hours straddle midnight and in late night schedules for TV and radio stations:
https://en.wikipedia.org/wiki/Date_a...ation_in_Japan

I have a feeling that referring to hours beyond 24 is just a thing that came about randomly / casually without a formal standard. But perhaps Wikipedia is right that there's an established convention that you can only count hours as far as 30.