This may be a dumb, uneducated question, but I'm honestly not sure when it started. Obviously cavemen didn't do this and maybe used the height of the sun in the sky at best. But when did people start formally (i.e. without thinking it's ok to arrive at a later time) arriving at any kinds of meetings at specific times (ex. 2:00 pm) like we do today? Like I think Romans had sundials, but did senators use that to arrive to debates at precise times of day? Or did they just kind of have sundials without using them in that way and relied more on general height of the sun in the sky? And if not the Romans, when do we arrive at a culture in time that uses hours to meet up at preordained times like ours?
Time as we know it - a discrete, measured and precise phenomenon - didn’t actually really exist until the development of the clock. Prior to this time was for the most part thought of in looser, more practical terms: days of the week and seasons.
As towns developed, the need to have a breakdown of the day developed as well. Indeed, the development of capitalism got the ball rolling for time in its modern form. As merchants moved around, as markets took shape, as daily life in the city became demarcated by regular events, the need to pinpoint these events grew.
The word clock actually has its origins in the Fench and German words for bell. This is because in pre-modern Times towns were “ruled by the bell”. Bells would ring out at time specific to religious happenings. In this way time was first really quantified and tracked by religious observers, though this knowledge didn’t really spread. And even in this regard, the religious weren’t necessarily concerned with precision so much as observance.
Clocks were first invented in the late 13th century, likely the 1270’s. At the time clocks were basically just bells on timers. They didn’t have a face or hands, and therefore still the notion of tracking and keeping time wasn’t widespread.
The fourteenth century was revolutionary in the progress of uniformity in time keeping Charles V of France decreed that all clocks in France keep the same time as his.
“It was in the European city that time began, for the first time in history, to be ‘isolated’ as a pure form, exterior to life.” AJ Gurevich
City dwellers around this time period were obsessed with clocks. Through the clock people learned that time was a quanta, not a continuous flow.
My guess would be that this became a widespread phenomenon in cities between 1350-1450 depending on the location.
Source: Alfred Crosby, The Measure of Reality
Thanks for the great, detailed responses everyone! I find it amazing that mechanical clocks are actually so old. I would have guessed they were an invention of the industrial revolution at best. I guess my next question is when the earliest written schedules are from using clock hours. Like when do we see, say, some kind of notebook with different events written out for a single day, like, "12:00 pm: lunch time, 1:30 pm: feed the horses," etc.?