Author Douglas Rushkoff suggests that the idea that time is money came from different perceptions of looking at and measuring time. He makes the distinction between calendar-driven and machine-driven civilizations.
He writes: “Thanks to the clock tower, the rhythms of daily life were now dictated by a machine. Over time, people conformed to ever more precisely scheduled routines. Where the priority of the calendar-driven civilization was God, the priorities of the clockwork universe would be speed and efficiency. Where calendars led to people to think in terms of history, clocks led people to think in terms of productivity. Time was money.”
Rushkoff mentions how this perception is reflected in our language noting that, “Only after the proliferation of the clock did the word “speed” (spelled spede) enter the English vocabulary, or did “punctual” – which used to refer to a stickler for details—come to mean a person who arrived on time.”
(Taken from Douglas Rushkoff, Present Shock: When Everything Happens Now, Penguin Group, New York, 2013, p. 81.)