The Babylonians, people who lived between 1950 BC and 539 BC, in Mesopotamia, were the first to mark the passage of time. When building the sundial, they divided the day into 12 parts and then into 24, which are the hours we still use today. “Since they used the duodecimal (based on the number 12) and sexagesimal (based on 60) numerical systems, the Babylonians divided the hour into 60 parts, ‘inventing’ the minute,” explains metrologist (specialist in measurement systems) Pedro Luiz Montini , from the Institute of Weights and Measures (Ipem-SP). “Dividing the minute into 60 parts, they arrived at the definition of the second, although it was only possible to detect it accurately centuries later”, he adds.
YEAR
In 46 BC, the Roman general Julius Caesar adapted the Egyptian calendar – from 3000 BC The Julian model divided the year into 365 days – equivalent to the known solar cycle at the time – and 12 months. In 1582 the pope
Gregory XIII corrected inaccuracies and established the current model, the Gregorian
MONTH
Babylonians, Egyptians and ancient Chinese divided the year into ten periods, named after their gods. The Romans were the first to divide the year into 12 parts. The names of the seventh and eighth months, however, were quinctillis and sextillis – July and August came later, in honor of Julius Caesar and Emperor Caesar Augustus
In AD 8, the Roman senate played a day from February to August. Is that the month of Caesar Augustus had one day less than that of Julius Caesar (July)
WEEK
The definition of the seven-day cycle has a twofold origin. On the one hand, astrologers from Alexandria, capital of Egypt around 300 BC, organized the days into groups of seven to follow the order of the seven known planets. On the other hand, the Hebrew tradition of the Sabbath, which establishes a day of worship every seventh, on which the Jews rested
The Sumerians already observed the seven-day cycle – related to the phases of the Moon – before the Egyptians and Hebrews, but without formalizing the system.
DAY
The Babylonians needed to measure time in fractions smaller than day and night. For this, they invented humanity’s first clock, the sundial. It still wasn’t possible to mark the hours precisely, but the shadow’s trajectory separated the day into 12 parts. With the same reasoning, they shared the night too
HOUR
The definition of hours, minutes and seconds was known since the Babylonians, but it took a while for someone to measure time accurately. The mechanical clock only appeared in the 14th century and slowed down by 15 minutes a day – one day every three months! In 1656, with the pendulum clock, the delay was reduced to one minute per week.
The second was equivalent to 1/60th of a minute until 1967, when the International System of Units defined its duration based on the radiation of the cesium 133 atom.
OTHER MEASURES
With technological advances, the need arose to measure smaller time intervals. This is the case of the microsecond (millionth of a second), the femtosecond (1 quadrillion times smaller than a second) and the attosecond (one thousand quadrillion times smaller than a second), the shortest time ever measured by scientists
Members of the French Revolution tried to introduce a decimal system for measuring time – in order to bring it into line with distance measurements.