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Time zone

Time zone


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Because of the Earth's rotation around its own axis, day and night alternate in each place. At all points along the meridian directly facing the Sun it is noon; in all those that lie along the opposite meridian, 180 away in length, it is midnight.

When the Sun is above the meridian of our city, it has obviously not yet reached the meridian of another city immediately to the West with respect to ours. It follows that astronomical noon varies from point to point for even neighboring places. From a rigorous point of view, each city should have its local time.

To regulate this matter, in 1884 an international agreement was reached by which the Earth is divided into 24 time zones, each comprising a band of 15 contained between two meridians. It was established to establish as a meridian of origin the one that passes through Greenwich.

The basis of the current time system is the so-called Greenwich mean time (abbreviated G.M.T.) or universal time (abbreviated U.T.). For example, Italy belongs to the second time zone also called the Central European Middle Time. All countries belonging to this zone adopt, by convention, a delayed time of one hour with respect to those that are part of the Greenwich meridian (first time zone). The time established in this way is also called civil time and does not necessarily correspond to true time, that is, astronomical.


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