User's Manual Part 2

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A P P E N D I X
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C HAPTER 2 U NIVERSAL C OORDINATED T IME
If the world were ideal, we would have one time the world over, and all
clocks would read the same. However, because our planet is divided
between day and night, our global structure has generally adopted solar
time. This divides the planet into a series of time zones. Although it makes
it easy to keep time based on daylight, it is very difficult for scientists,
pilots, military, and others to use.
Another complication is the occurrence of Daylight Saving Time in
selected areas. Navigation, exchanging data, astronomy, synchronization
of experiments, and other fields require a single means by which to keep
time.