The duodecimal system has the number 12 as its base. Let’s take a look at its origin:

Egyptians were using and developing sundials to tell time, and many historians believe they were the first ones to divide the day into smaller parts. The T-shaped sundial that they invented could split the time between sunrise and sunset into 12 parts. This division has roots in the use of the duodecimal system, which uses 12 as a base. The significance of this system probably comes from the number of lunar cycles in a year or from the sum of all finger joints (excluding the thumb). By summing up the joints on the other 4 fingers, they were able to count up to 12.
Another interesting observation that Egyptian astronomers made was the arrangement of 36 stars in the sky that divided the circle of the heavens into equal parts. During the 2 twilight periods, there were 3 stars that, each time, weren’t visible. So the remaining 12 stars could be seen in the time of complete darkness, which led to the division of the night into 12 parts.

Note: The concept of the 24-hour day was first proposed in the Hellenistic period by Hipparchus. He also noticed that there were 12 hours of light and 12 hours of darkness on equinox day. But, to be precise, because of the refraction of the atmosphere, the typical daylight time is actually slightly longer than 12 hours by 7 minutes.

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