Talk:International Atomic Time

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Contents 1 It's a coordinate time, not a proper time 2 32 vs 22 seconds difference 3 and New Zealand have whole hour plus 45 minutes offsets from UTC. 4 Leap second scheduled for the end of the year 5 Union Square NYC

[edit] It's a coordinate time, not a proper time

I wish to point out the content of http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1986CeMec..38..155G The abstract alone makes it clear that TAI is a coordinate time, not a proper time. The article itself immediately cites the CIPM approved statement by the CCDS which asserted that it is a coordinate time. Steven L Allen 07:21, 27 November 2006 (UTC)

[edit] 32 vs 22 seconds difference

The TAI article says that UTC is 32 seconds away from UTC, while the leap seconds article lists 22 leap seconds that have been inserted (and the one for the end of 2005). Where's the discrepency from?

TAI was established on 1 January 1958 to be equal to UT1. UTC was established on 1 January 1972 with an inital offset of 10 seconds from TAI to account for all variations in broadcast time between 1958 and 1972, much of it in the form of artificially lengthened seconds. During that period, the time between any two 'ticks' of broadcast time was slightly longer than one atomic second. Since 1972 broadcast time signals have had exactly one atomic second between any two ticks. In a manner of speaking, the extra length that used to be added to every second is saved up until one whole second is reached. Since 1972 22 of these whole atomic leap seconds have been inserted. This info as well as additional info should be in these articles. — Joe Kress 07:56, 12 July 2005 (UTC)

[edit] and New Zealand have whole hour plus 45 minutes offsets from UTC.

But NZ standard time is +12:00hrs from UTC. There was a half-hour shift during World War 1, similar to daylight saving, but it was permanent, year-round and thus merely offsets the NZ time zone to the longitude. (NZ is not bisected by 180 degrees) - Regards, NickyMcLean (in Wellington, NZ)

That paragraph is poorly worded. The New Zealand 45 minute offset refers to the time of Chatham Islands at UTC+12:45, not to New Zealand proper. Australia has a total of four half hour offsets, one in Australia proper and three for dependent islands, but no 45 minute offset. In any case, that paragraph is not germane to the article, so I'm removing it. — Joe Kress 04:51, 14 September 2005 (UTC)

[edit] Leap second scheduled for the end of the year

There is a leap second scheduled to occur at the end of the year (2005-12-31T23:59:60), so that the article should probably be changed to read UTC = TAI - 33 seconds somewhere around that time.

The announce can be found at http://hpiers.obspm.fr/iers/bul/bulc/bulletinc.dat, or linked via http://tycho.usno.navy.mil.

[edit] Union Square NYC

Is there any source to suggest that the clock in Union Square is synced to an atomic time server somewhere? Couldn't it just be a clock?

There doesn't seem to be mention of it in the artists fact sheet.

Blckdmnd99 13:13, 25 March 2007 (UTC)

• A simple Google search will answer the question for you, but here is one hit: http://alcorn.com/cases/metronome/index.html. Googling is a great way to find some of these answers. --David Shankbone 13:50, 25 March 2007 (UTC)

Well how about that. I hunted around a good deal but mostly on the artists site. This definitely supports the atomic bit, thanks for pointing it out. Blckdmnd99 02:29, 27 March 2007 (UTC)

My pleasure - it was a good question. --David Shankbone 02:40, 27 March 2007 (UTC)

• The description states "It receives its timing reference from the atomic clock at the US Navel Observatory in Washington DC." This is largely true of most computers in the United States although there is a distinction between the civilian NIST time signal and the USNO time signal. If this is just a computer that is synchronzing using NTP that it hardly is appropriate to include a picture to illustrate an atomic clock. You could just as easily include a picture of my PC or a commercial "Atomic Clock". I would recommend removal of this image from this page in favor of something more explicative value. PaigePhault 04:54, 27 March 2007 (UTC)
  • I'd like you to provide a source that most computers in the United States are synced to atomic time. Like it or not, the metronome is an atomic clock and there are more Google hits that confirm that; I only provided one. Now you provide one showing it is not. --David Shankbone 12:56, 27 March 2007 (UTC)

Well, the majority (>80%) of computers are running Windows XP and by default Windows XP enables time synchronization with NTP. Microsoft maintains its own time server synched to NIST's atomic clock. There were problems with this implementation in the past, but that was 6 years ago. I am quoting from the very source you provided - it says specifically that it is a Alcorn McBride V4+ Show controller synchronized to NIST's clock in Washington DC. So like it or not (and I don't like it) the Metronome is not an atomic clock. PaigePhault 20:11, 27 March 2007 (UTC)

I tend to agree with PaigePhault. The caption for the photo says "Atomic Clock overlooking Union Square, New York City" but that is incorrect; the Union Square "Metronome" is not itself an atomic clock; it merely receives its time reference from an atomic clock. But aside from that, this is an article on "International Atomic Time" (not atomic clocks). Even if the Metronome were a true atomic clock, it would not be a suitable illustration for this article because what it displays is not TAI but civil time in New York City. My suggestion would be to remove that illustration from this article, but instead insert it in the article North American Eastern Time Zone. --Mathew5000 22:32, 27 March 2007 (UTC)

Okey-doke. --David Shankbone 23:07, 27 March 2007 (UTC)