Talk:Civil time/Archive 1

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)

Too many solar time articles

Please see Wikipedia talk:WikiProject Time#Too many solar time articles Jc3s5h (talk) 17:36, 2 August 2011 (UTC)

Greenwich Civil Time

The term "Greenwich Civil Time" is used, without definition or link. What, therefore, can it mean? 94.30.84.71 (talk) 12:06, 14 March 2016 (UTC)

The sentence the term appears in makes the meaning fairly clear, but maybe the wording should be improved. In that sentence, "Greenwich Civil Time" (GCT) means Greenwich Mean Time (GMT) with the understanding that the day begins at midnight. Until 1924 astronomers and astronomical almanacs considered days of GMT to begin at noon, but the general population considered days of GMT to begin at midnight. Beginning in 1925 the astronomers surrendered and started the day from midnight. The US Naval Observatory felt the term GMT was now too ambiguous to use in their publications, and created the term GCT.

Maybe this point is too obscure for the lead and should be relegated to the body of the article. Jc3s5h (talk) 14:08, 14 March 2016 (UTC)

If only the article had a body :) ~Kvng (talk) 21:56, 18 March 2016 (UTC)

RN Time

The second paragraph discources about older Astronomical Time. If that is sufficiently on-topic, there should at least be a reference to older RN time, which was half a day ahead of local time (mean or solar?) until about the date of the Battle of Trafalgar. 94.30.84.71 (talk) 09:09, 15 June 2016 (UTC)