Europe around 20,000 years ago recorded days between successive new moons. Anoth-
er hypothesis states that the measurement of time dates back some 10,000 years,
which coincides with the development of agriculture, especially in terms of when to
best plant crops. Still others point to timekeeping evidence dating back 5,000 to 6,000
years ago around the Middle East and North Africa. Whatever the true beginnings,
most researchers agree that timekeeping is one of those subjects whose history will
probably never be accurately known.What culturetook the first steps toward timekeeping?
Around 5,000 years ago, the Sumerians in the Tigris-Euphrates valley (today’s Iraq)
appear to have had a calendar, but it is unknown if they truly had a timekeeping
device. The Sumerians divided the year into months of 30 days; the day was then
divided into 12 periods (each corresponding to two of our modern hours) and the peri-
ods into 30 parts (each corresponding to four of our minutes).Overall, many researchers agree that the Egyptians were the first serious timekeep-
ers. Around 3500 BCE, they erected obelisks (tall, four-sided monuments), placing them
in specific places in order to cast shadows as the Sun moved overhead. This thus creat-
ed a large, crude form of a sundial. This sundial time was broken into two parts: before
noon and after noon. Eventually, more divisions would be added, breaking down the
time units even more into hours. Based on the length of the obelisks’ shadows, the
56 huge sundials could also be used to determine the longest and shortest days of the year.
How did our present day become divided
into hours, minutes, and seconds?D
ivisions into hours, minutes, and seconds probably began with the Sumeri-
ans around 3000 BCE. They divided the day into 12 periods, and the periods
into 30 sections. About one thousand years later, the Babylonian civilization,
which was then in the same area as the Sumerians, broke the day into 24 hours,
with each hour composed of 60 minutes, and each minute having 60 seconds.It is unknown why the Babylonians chose to divide by 60 (also called a base
number). Theories range from connections to the number of days in a year,
weights and measurements, and even that the base-60 system was somehow eas-
ier for them to use. Whatever the explanation, their methods proved to be
important to us centuries later. We still use 60 as the basis of our timekeeping
system (hours, minutes, seconds) and in our definitions of circular measure-
ments (degrees, minutes, seconds). (For more information about the Sumerian
counting system, see “History of Mathematics.”)