Talk:Civil time

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[edit] Agree on time

It deserves to be pointed out that there is one principal lesson which must be learned from the 1884 International Meridian Conference and all subsequent activity by the authorities in charge of determining and disseminating civil time: In a technological society with global telecommunications and transport we have to be able to agree on what time it is. What the IMC did not make clear was how precisely we need to agree, and whether the answer to that question differs for various users of time. Steven L Allen 18:19, 30 April 2007 (UTC)

The IMC did make clear that all users of time should begin their Universal Day at midnight, eliminating the 12-hour difference between civil time and astronomical time (and nautical time). At the time, no "global telecommunications" existed. Astronomical time was finally changed to match civil time in 1925. Astronomical time remained in universal use for all users of time until 1960. Then atomic time was disseminated until 1972, always adjusted to closely match astronomical time at the Royal Observatory at Greenwich. Only in 1972 did two forms of time emerge: UTC with one second ticks and leap seconds for civil users and a delta T correction of ±0.7s to the nearest tenth of a second for nautical users to more closely approximate the preceding astronomical time (the Soviet Union's delta T was to the nearest hundreth of a second). With the near universal use of GPS positioning systems since 2000, the delta T correction is no longer needed, leaving only one kind of time to the nearest second. Some tried to eliminate leap seconds recently, but did not succeed. And GPS does not recognize leap seconds, but its time is not "disseminated", so it does not count. I do not see any disagreement on "disseminating civil time" for different users. — Joe Kress 23:14, 30 April 2007 (UTC)