Time Calculator
Time Calculator
Add or subtract time values with this easy-to-use calculator. Input fields can be left blank for zero values.
Time Calculator
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The History and Concepts of Time
Ancient Greece
There exist various concepts of time that have been postulated by different philosophers and scientists over an extensive period of human history. One of the earlier views was presented by the ancient Greek philosopher Aristotle (384-322 BC), who defined time as "a number of movement in respect of the before and after." Essentially, Aristotle's view of time defined it as a measurement of change requiring the existence of some kind of motion or change.
He also believed that time was infinite and continuous, and that the universe always did, and always will exist. Interestingly, he was also one of the first people, if not the first person, to frame the idea that time existing of two different kinds of non-existence makes time existing at all, questionable. Aristotle's view is solely one amongst many in the discussion of time, the most controversial of which began with Sir Isaac Newton, and Gottfried Leibniz.
Newton & Leibniz
In Newton's Philosophiæ Naturalis Principia Mathematica, Newton tackled the concepts of space and time as absolutes. He argued that absolute time exists and flows without any regard to external factors, and called this "duration." According to Newton, absolute time can only be understood mathematically, since it is imperceptible. Relative time on the other hand, is what humans actually perceive and is a measurement of "duration" through the motion of objects, such as the sun and the moon. Newton's realist view is sometimes referred to as Newtonian time.
Contrary to Newton's assertions, Leibniz believed that time only makes sense in the presence of objects with which it can interact. According to Leibniz, time is nothing more than a concept similar to space and numbers that allows humans to compare and sequence events. Within this argument, known as relational time, time itself cannot be measured. It is simply the way in which humans subjectively perceive and sequence the objects, events, and experiences accumulated throughout their lifetimes.
Einstein's Revolution
While many scientists contributed to what would ultimately transform theoretical physics and astronomy, the scientist credited with compiling and describing the theory of relativity and the Lorenz Transformation was Albert Einstein. Unlike Newton, who believed that time moved identically for all observers regardless of the frame of reference, Einstein, building on Leibniz's view that time is relative, introduced the idea of spacetime as connected, rather than separate concepts of space and time.
Einstein posited that the speed of light, c, in vacuum, is the same for all observers, independent of the motion of the light source, and relates distances measured in space with distances measured in time. Essentially, for observers within different inertial frames of reference (different relative velocities), both the shape of space as well as the measurement of time simultaneously change due to the invariance of the speed of light – a view vastly different from Newton's.
How We Measure Time
There are two distinct forms of measurement typically used today to determine time: the calendar and the clock. These measurements of time are based on the sexagesimal numeral system, which uses 60 as its base. This system originated from ancient Sumer within the 3rd millennium BC, and was adopted by the Babylonians.
Base 60 is used due to the number 60's status as a superior highly composite number having 12 factors. A superior highly composite number is a natural number, that relative to any other number scaled to some power of itself, has more divisors. The number 60, having as many factors as it does, simplifies many fractions involving sexagesimal numbers, and its mathematical advantage is one of the contributing factors to its continued use today.
Development of Time Units
The Egyptian civilization is often credited as being the first civilization that divided the day into smaller parts, due to documented evidence of their use of sundials. The earliest sundials divided the period between sunrise and sunset into 12 parts.
Hipparchus also developed a system of longitude lines encompassing 360 degrees, which was later subdivided into 360 degrees of latitude and longitude by Claudius Ptolemy. Each degree was divided into 60 parts, each of which was again divided into 60 smaller parts that became known as the minute and second respectively.
Early Timekeeping Devices
Early devices for measuring time were highly varied based on culture and location, and generally were intended to divide the day or night into different periods meant to regulate work or religious practices. Some of these include oil lamps and candle clocks which were used to mark the passage of time from one event to another, rather than actually tell the time of the day.
The water clock, also known as a clepsydra, is arguably the most accurate clock of the ancient world. Clepsydras function based on the regulated flow of water from, or into a container where the water is then measured to determine the passage of time.
The first pendulum mechanical clock was created by Christiaan Huygens in 1656; it was the first clock regulated by a mechanism with a "natural" period of oscillation. Today however, atomic clocks are the most accurate devices for time measurement. Atomic clocks use an electronic oscillator to keep track of passing time based on cesium atomic resonance.
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