# How did people count seconds before clocks were invented?

How did people count seconds? How did people count minutes? How come that every second of a clock takes exactly as much time as needed to be 86400 to fulfill 24 hours and 31536000 to fulfill a year? How was time divided when people didn't have any electricity or devices to count time with? I've heard of the Roman clock (is that what it's called) and hourglasses, but those don't explain how someone could actually divide time. How did people divide an exact day to 24 hours, then 60 minutes and then 60 seconds to get exactly as much as they needed? And when they counted it correctly, how did they redo the count? Did musicians maybe remember how long a second lasts as they have rhythmical talent? I really don't understand how people actually made clocks. I don't even know if this question exists and where on StackExchange.

Does anyone have any idea?

• See e.g. Roman timekeeping. There were not "precise" measurement. Seconds were astronomical measure; for daily life nothing was used: maybe heartbeat... Commented Feb 5, 2017 at 21:45

1. Electricity has nothing to do with the question. Clocks which could count minutes and seconds were purely mechanical and precise mechanical clocks (which could count seconds reliably) were invented in 18th century. Until 1970s most wristwatches were mechanical. They are available nowadays as well but good ones are expensive.

2. People did not count minutes and seconds before the wide spread of mechanical clocks. They counted only hours (using halves and quarters of an hour when necessary). In the rare cases when short intervals had to be measured they used heartbeats. (Galileo in his early experiments with pendulum used his heart to measure short time intervals). Galileo actually invented the pendulum clock which made it possible to measure minutes. It took about a century after that to increase the accuracy to seconds.

3. Nevertheless the notion of minute and second existed. It was used by astronomers. For example they could measure the length of the year (and other astronomical intervals) with high precision. But this was not done with clocks. This was done by very long observations. Suppose you know that 100 years=N days, then 1 year is approximately N/100 days, with accuracy 1/100 day. As it is possible to measure the moment of beginning of the year (say spring equinox) within one hour, without any clocks, if you have two measurements 100 years apart, you can compute the length of the year with 1/100 of an hour accuracy. This is why astronomers invented minutes and seconds, long before they came into common use.

• A good answer, especially point 3. Just to clarify one thing: Ptolemy (for example) expressed the length of the year not in days, hours, minutes, seconds, but as days, and sexagesimal fractions thereof.
– fdb
Commented Feb 18, 2017 at 21:49

How did people count seconds before clocks were invented?

In general, they didn't, because there was no need to to so.

The need for accuracy to the level of a second or less is a very recent need. Before the invention of trains and telegraphs, there was no need for even hour level accuracy, let alone minute or second level accuracy. Whether the roads were dry or muddy could spell the difference between being days early versus days late (or sometimes weeks late) for an appointment.

• Minutes and seconds were important in celestial navigation in the late 18th century, when accurate marine chronometers were available. Commented Nov 12, 2021 at 18:53

They didn't. The first person to divide time into 24 hours/60 minutes/60 seconds was the scholar al-Biruni (973 - ~1050) who lived in what is now Uzbekistan. He invented the concept in about 1000 as a way to subdivide the pattern of Jewish lunar cycles.

Seconds could not be reliably measured until the invention of the mechanical clock around 1500, and people simply didn't try. Once clocks were in widespread use, there was a concerted effort to measure time accurately at the seconds level, notably for use in navigation/longitude determination.