“Do you have a minute to talk about time?” isn’t a sentence you would hear in Ancient Egypt, mostly because they had no concept of a stable measure of time, such as an hour, minute, or second. In fact, it took until the Ancient Babylonians and Greeks for even the concept to show up, and until the invention of mechanical clocks for it to become standard.

The **Babylonians** contribution to modern time was the “sexagesimal” system—the numbering system we use to tell time today. This system operates off of what mathematicians call “base 60″—a mathematical structure that counts from 1-60 (the Babylonians weren’t crazy about the number 0). In contrast, the decimal system that we use for almost everything else uses base 10—just the numbers 0-10—but we keep the sexagesimal system around for three things: measuring time, measuring angles, and finding geographical coordinates.

The **Ancient Sumerians** invented the sexagesimal system in the third millennium B.C, but it was the Babylonians who, much later, brought it into use in their mathematical and astronomical systems. No one is exactly sure why they chose it, but a likely reason is that 60 is what mathematician’s term a “superior highly composite number,” meaning that it can be divided by a lot of other numbers—12 of them, in this case. This makes it very easy to quickly measure things—you can divide 60 into halves, thirds, fourths, fifths, and sixths—so it actually makes objective sense for us to be using this system to measure time and geometric angles, which are two things that by their very nature are divisions.

The first example we have of a time measurement device comes from Ancient Egypt—some time in the second millennium B.C—but they did not use sexagesimal units; they used something called the “**duodecimal system**,” or base 12, to divide the day and night into 12 units each, which is where we get our current 24-hour system. these units, however, did not have fixed lengths, but changed with the lengths of the days and nights. To civilizations without easily available artificial light, what really mattered was the amount of daylight, so in the winter an Egyptian hour could be as short as 53 minutes, while in the summer it could go as long as 67 minutes. In Northern England, with its high latitude, this ratio could go from 30 minutes per hour in the winter to 90 in the summer. This relative method of measuring time would continue being used until medieval times.

**Hipparchus**, a second-century B.C Greek astronomer was the first Greek to combine day and night into a unified 24-hour cycle with fixed-length hours. He also used the sexagesimal system to create lines of latitude and longitude with 360 total degrees, which Claudius Ptolemy, in 150 A.D, divided into groups of sixty (minutus primae), and then again into another sixty parts (minutus secundae); these terms are the direct roots of the modern words “minute” and “second”. These were still primarily geometric measures, though, not timekeeping ones.

The two primary obstacles to the adoption of fixed units of time were that common people still found relative measurements more useful, and that measurement techniques were still fairly imprecise. While water clocks—devices that measured time by keeping water flowing at a constant rate from one vessel to another—had been in use since Ancient Egypt, and continued to be refined all the way up to medieval times, they did not provide a high enough level of consistency to make empirical units possible.

Indeed, even when mechanical clocks appeared in 14th-century Europe, the early ones almost never used minutes, sticking instead with keeping track of hours, sometimes dividing them into quarters or thirds, but still not making use of the sexagesimal system. It was only, in fact, with the invention of the pendulum clock in the 16th century that minutes and even seconds became the universal norm, as clocks were now precise enough to make consideration of that small a unit of time practical, and Babylonian math finally found its way onto clock faces.

Thus, though the Babylonians did not invent modern time, they provided the means to measure it. When you look at a clock, you are seeing the product of thousands of years of different civilizations building on the same system. 4,000 years ago, the system you now use for telling time was invented, and it took almost 3,500 of those years for the system itself to be refined to the one we use today. Having this precise of a timekeeping system is one of the things that has enabled the existence of the modern age, giving us ways to measure efficiency, schedule events more precisely, et cetera—and we owe it to a wide range of people spread across the millennia.