
This article explores the history of time measurement, beginning with ancient civilizations like the Sumerians and their development of calendars. It discusses the challenges in harmonizing civil timekeeping with astronomy, including sidereal and solar years, and the division of days into hours. The article also covers the Roman and early Christian calendars, highlighting their inaccuracies and the historical attempts to reform them, such as the Julian and Gregorian calendars and the fixing of Easter.