The Clock
The moonshaped analog clock shows a whole half-day, it's easy to look back or ahead because an entire chunk of the day appears on its face.
Analog clocks say NOW, and only now; they completely filter out past and present.
In our personal scheduling we tend to use "clock shorthand" by making appointments ON THE HOUR, i.e., "ALPB meets at 8."
The broadcast world latched onto clock time just like coins and nails clamp to metal detectors: "Atrain Radio starts at 7 on WCFI."
Radio programs inherited their length as virtual pizza slices cut from the hour: 60-minutes; 30-minutes; 55-minutes; 5-minutes.
Obedience to "the top of the hour" as the main meeting point rises out of convenience... imagine saying "Join us promptly at 2:38." We might not be able to do it.
In my mini-essay on CLOCKS the second paragraph should say "Digital clocks say NOW."
Digital.
Digital.
I'd be a good writer if I was.