Constructed Time Standards
International Atomic Time (TAI) is the primary international time standard from which other time standards, including UTC, are calculated. TAI is kept by the BIPM (International Bureau of Weights and Measures), and is based on the combined input of many atomic clocks around the world, each corrected for environmental and relativistic effects. It is the primary realisation of Terrestrial Time.
Coordinated Universal Time (UTC) is an atomic time scale designed to approximate Universal Time. UTC differs from TAI by an integral number of seconds. UTC is kept within 0.9 second of UT1 by the introduction of one-second steps to UTC, the "leap second". To date these steps have always been positive.
Standard time or civil time in a region deviates a fixed, round amount, usually a whole number of hours, from some form of Universal Time, now usually UTC. The offset is chosen such that a new day starts approximately while the sun is at the nadir. See Time zone. Alternatively the difference is not really fixed, but it changes twice a year a round amount, usually one hour, see Daylight saving time.
Read more about this topic: Time Standard
Famous quotes containing the words constructed, time and/or standards:
“The greatest, or rather the most prominent, part of this city was constructed with the design to offer the deadest resistance to leaden and iron missiles that might be cast against it. But it is a remarkable meteorological and psychological fact, that it is rarely known to rain lead with much violence, except on places so constructed.”
—Henry David Thoreau (1817–1862)
““Come, come” said Tom’s father, “at your time of life,
There’s no longer excuse for thus playing the rake—
It is time you should think, boy, of taking a wife.”
“Why, so it is, father—whose wife shall I take?””
—Thomas Moore (1779–1852)
“As long as our people quote English standards they dwarf their own proportions.”
—Ralph Waldo Emerson (1803–1882)