Danna (Mesopotamian)

Danna (Sumerian) or Beru (Akkadian) is a word denoting a unit of time consisting of two hours. There were twelve Danna in a day. Danna were first used around 2400 BC.

Change in length and decline
In Hellenistic times the Danna was halved with the introduction of the temporal hours and the number of daylight hours increased from twelve to twenty-four. The conversion was based on the ancient Egyptian precursors of the 24 seasonally - equal hours. A 24-hour division of the day could not be proven in inscriptions on Babylonian tablets, which is why the Babylonians cannot be used as the originators of the 24-hour division of the day.