SI Unit of Time

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What is the SI unit of time?

Official definition of a second

In 1967 a new SI definition of a second was created based on the radiation from the caesium-133 atom.

It is correctly defined as "the duration of 9,192,631,770 periods of the radiation corresponding to the transition between two hyperfine levels of the ground state of the caesium-133 atom."

News:

USA & Canada clocks
on Standard Time until:
Sunday 11 March 2012 2am local time

Europe / UK clocks
on Standard Time until:
Sunday 25 March 2012 01:00 GMT

UK clocks change trial being considered
Have your say YES or NO

Australia clocks
on Daylight Saving Time

Cuba will end DST two weeks later this year
Delayed to 13 November 2011 at 01:00

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Greenwich Mean Time

Greenwich Mean Time (GMT)

GMT-1 | GMT-2 | GMT-3 | GMT-4 | GMT-5 | GMT-6 | GMT-7 | GMT-8 | GMT-9 | GMT-10 | GMT-11 | GMT-12
GMT-0 | GMT | GMT+0
GMT+1 | GMT+2 | GMT+3 | GMT+4 | GMT+5 | GMT+6 | GMT+7 | GMT+8 | GMT+9 | GMT+10 | GMT+11 | GMT+12 | GMT+13 | GMT+14

Time Zones

Africa, Asia, Australia, Canada, Caribbean, Europe
European Union, Pacific / Oceania, Russia, South America, UK, USA

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SI Unit of Time