Time Zone Conversion

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What is Time?

It's a question we have all considered - but one that isn't so easy to answer. In a world where time is money and "good time management skills" feature on every job description, we are all obsessed with time. But have you considered what it really is?

A scientific concept of time
In everyday life, "time" generally refers to the time of day, that is, the number of hours, minutes and seconds that have passed since midnight. In the UK we express time using Universal Time (UT), often referred to as Greenwich Mean Time (GMT). The time of day varies across the globe, according to time zones created to avoid the confusion of myriad local times. This sort of time is clearly measurable, and we might say that it represents a scientific approach to time.

Scientists, or realists, would argue that time is fundamental and universal – an entity that we can quantify. In physics, time and space are closely linked, and the past and future are clearly defined categories. For scientists, time is in fact a fourth dimension - integral to Einstein's theories of relativity. "Spacetime" is a mathematical model that combines the three spatial dimensions (length, height and width) with time. Spacetime is made up of events - an event being a unique location at a unique time, like a cannon being fired or a single heartbeat. Theoretical physicists use spacetime to describe and develop theories about our universe, and they argue that it exists independently of any observer.

Philosophical approaches
Philosophers have debated the meaning of time for centuries. Aristotle believed that time was the measure of change, but many philosophers have shied away from this definition, emphasising instead the relationship between the event and the observer. Think how slowly time seems to pass on a Friday afternoon when you can't wait for the weekend, or how excruciatingly long a couple of seconds appear if you're carrying a hot plate! These are simple examples that seem to demonstrate the non-uniform nature of time, the way it alters depending on our circumstances.

It was this quality of time that Kant was referring to when he defined time as "a way of structuring our experience of things". Leibniz also believed time to be a framework or a tool for comprehending events. According to these theories, time is not fixed in a scientific sense, but essentially arbitrary. Time is a way of understanding the world which is shaped by human society rather than operating independently of it.

Measuring time through the ages
Yet these contrasting scientific and philosophical approaches are both fairly modern. Past societies have undoubtedly considered time in a vast number of ways, only some of which we know of through archaeological and historical sources.

In the second millennium BC, water clocks were used in several parts of the world to mark the passing of time. The simplest of these clocks were bowl-like vessels with a hole in the bottom. The water dripped or trickled out of the hole at a constant rate, and the amount of water remaining indicated the time. Earlier still, around 2500BC, sundials were being used to measure time in Egypt. These were simple shadow poles, or gnomons. Made of stone or wood, the length of the shadow they cast allowed ancient Egyptian society to divide the day into 24 units - what we now call hours.

Why 24 hours? Sumer, a civilisation contemporary with Ancient Egypt, developed a counting system based on 12 - this being the number of "segments" visible on the fingers of one hand. One hand (12 segments) referred to daylight, and another covered the 12 hours of darkness. Later, the hand system was combined with Babylonian mathematics, which was based on the figure 60. So if you've ever wondered why there are 60 seconds in a minute, 60 minutes in an hour, and 24 hours in a day...you can thank the ancient civilisations of Sumer and Babylonia!

In the longer term, prehistoric peoples were aware of the passage of time through their observation of celestial bodies. A year as a unit of time came about because the sun rises and sets 365 times before all the constellations return to exactly the same position in the sky. The precise day on which calendars began in ancient societies might be governed by the rising of a particular constellation. The Aztec calendar, for example, began on the day the Pleiades rose.

How do we accurately measure time today?
Time in the modern world is measured by around 300 atomic clocks, located in different world regions. The average value of these clocks is the basis of International Atomic Time, which is used to calculate Universal Time (UT). The National Physical Laboratory in the UK houses atomic clocks which are accurate to within one second in three million years.

Is time a matter of cultural difference?
Even if we have prehistoric evidence of how time was measured, we can't know for sure how our ancestors thought about time. Anthropologists can give us some clues, however.

Did you know that Australian Aborigines have a notion called "Dreamtime", in which they simultaneously experience the past, present, and future? This co-existing time is considered by Aborigines to be more objective than linear time. This challenges our European concept of time.

Karl Marx argued that our modern idea of "clock time" allowed people to be exploited in a capitalist society. Marx believed that time became a commodity in capitalist societies. Work was equated with a specific period of time, rather than the accomplishment of a task. The control and regulation of time eroded the occupational calendars observed by farmers, fishermen and other workers.

Religions, too, have different takes on time. In Islamic and Christian traditions, time is linear. Other belief systems, such as Buddhism, are based on a cyclic existence, in which birth, life and death are followed by rebirth.

So the measurement and comprehension of time appear culturally specific. Even in today's globalised society, religion and social traditions influence our answer to the question "what is time?".
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