Time

Definition 1:

A continuous, measurable quantity in which events occur in a sequence proceeding from the past through the present to the future.

Definition 2:

The measured or measurable period during which an action, process or condition exists or continues.

Definition 3:

A dimension in which events can be ordered from the past through the present into the future, and also the measure of duration of events and the intervals between them.

ACCORDING TO archaeological evidence, the Babylonians and Egyptians began to measure time at least 5,000 years ago, introducing calendars to organize and coordinate communal activities and public events, to schedule the shipment of goods and, in particular, to regulate cycles of planting and harvesting. A Chronicle Of Timekeeping - Scientific American

Time has no physical properties to measure. What we are really measuring is time intervals, the duration separating two events. Throughout history, people have recorded the passage of time in many ways, such as using sunrise and sunset and the phases of the moon.

The inventions of timepiece technology include the Galileo Galilei's discovery of the isochronism of pendulums in Italy around 1582 and the Dutch Christiaan Huygens' invention of a pendulum clock by leveraging the principle around 1656.

The measurement of time began with the invention of sundials in ancient Egypt some time prior to 1500 B.C. However, the time the Egyptians measured was not the same as the time today's clocks measure. For the Egyptians, and indeed for a further three millennia, the basic unit of time was the period of daylight.