This has an important meaning for the number 12. First, before explaining 24, let me explain the number 12.
Long ago, people made a calendar by looking at the moon. The moon waxes and wanes, returning to its original position in about 30 days. In other words, the reason why a month is about 30 days is because of the ideas of the ancient people who made the calendar by looking at the moon.
Also, the moon repeats one cycle of 30 days, and if this cycle is repeated 12 times, it will be about one year. People in ancient times knew that the phases of the moon repeat 12 times to make a year. Therefore, the number 12 was considered to be a very important number for dividing things.
Therefore, the number 12 was used to determine the number of days, or time periods. This number was first determined by the people who lived in Mesopotamia.
However, those who lived in Egypt divided the day into night and day, and then divided each into 12 parts. The day is 12 hours long, and the night is 12 hours long, making a total of 24 hours in a day. The number 24 was then derived, and the day became a 24-hour day.
The reason why the 24-hour day is still in use today is that the method devised by the Egyptians in ancient times has been in use for a long time.