Who divided the day to 24 hours?

Answer 1

The 24 hour day and 60 minute hour originated with the Babylonians, who based their calendar on the earlier Sumerian and, perhaps, Egyptian calendars. The Encyclopedia Britannica has a number of good articles on this subject, and there is a wonderful chapter by Daniel J. Boorstin in "The Discoverers". As Boorstin explains, the history of timekeeping is itself lost in time.

The origin of a counting system based on 60 is related to astronomical cycles in the earth-moon-sun system. The earth takes about 360 days to orbit the sun, and over the course of a year the moon goes through about 12 cycles. Our life today is not very well keyed to these astronomical periods, but following and understanding the flow of the seasons was a great deal more important in earlier societies.

The Sumerians were probably the first to develop a calendar based entirely on the phases of the moon. The Babylonians refined this idea to form a calendar of which several details survive in our "modern" calendar. A Babylonian month began on the first day of a new moon. There are slightly more than 12 Babylonian months in a year (about 12.37 to be more precise). [Every two or three years, the royal astronomers would insert an extra full month into the calendar…so that the calendar based on the moon's cycles would stay in better sync with the year]-

From the fact that there are about 12 lunar months in a solar year, the Babylonians decided that the number 12 is the logical number by which time should be further divided. -From about 300BC, the Babylonians used a hemispherical sundial-type device to keep time during the day. The shadow cast by a thin rod would travel past 12 equally spaced marks on the inside of a hemisphere. The time it took for the shadow to pass from one mark to the next was ONE HOUR. Thus there were 12 hours during daylight. The night time was also divided into 12 parts, as timed most likely by water clocks…the other type of Babylonian clock. (Note that this Babylonian system yields hours which are shorter during winter.when the days are shorter.and longer in summer. As a result, in Babylon, in modern-day Iraq, the daylight hours in mid-winter were only ⅔ as long as the mid-winter night time hours with the opposite situation occurring in mid-summer.

The invention of accurate mechanical clocks at the end of the 13th century finally made the variable-length hour less useful than the modern hour of unchanging duration.-The Babylonians divided the hour into 60 minutes (60 = 5×12….that preferred number 12 appears again).