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(reminder: all quotes here are fiddled, probably.)

UTC (備忘)


LOD = length of day
TAI = International Atomic Time
UTC = Coordinated Universal Time
GMT = Greenwich Mean Time (basically UT1)

rotational speed of the earth is not uniform.
LOD fluctuates.

rotational speed is also slowing down on average.
LOD increases at a rate of about 1.7 ms/cent.

LOD = 86400 s (GMT, by definition)
= 86400 s (TAI in 1820)
= 86400.002 s (TAI at the end of 20th cent)
= 86400.004 s (TAI at the end of 21th cent)

1 day (GMT) is defined to be LOD.
1 day (TAI) is defined to be 86400 s (TAI).
LOD = 1 day (GMT) =/= 1 day (TAI), except in 1820

timestamp:
UTC = TAI with correction = a close approx. of GMT (+/-1s)
1 s (UTC) = 1 s (TAI) by definition
correction = leap second at irregular intervals
(+1s/500day at the end of 20th cent, on avaerage)
(+1s/250day at the end of 21th cent, on avaerage)

leap second announced:

wikipedia

2 Comments:

:: Blogger C.D (16.08.07, 10:24   ) sagt...

^.^

D.



:: Blogger sf (16.08.07, 18:08   ) sagt...

?

sf



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