Posted by
timothy
on from the seconds-all-taste-the-same dept.
ygslash writes "The IERS has announced today that, after seven years, there will once again be a leap second this year. On December 31, 2005, the time 12:59 will last for 61 seconds."
Re:Shouldn't that be...
by
dextr0us
·
· Score: 4, Informative
A positive leap second will be introduced at the end of December 2005.
The sequence of dates of the UTC second markers will be:
2005 December 31, 23h 59m 59s 2005 December 31, 23h 59m 60s 2006 January 1, 0h 0m 0s
Actually, its 12:00:00 then another 12:00:00.
-- "Martha Stewart can lick my Scrotum......do i have a scrotum?" -- Sharon Osbourne
Re:I have an atomic watch!
by
iggymanz
·
· Score: 2, Informative
hah, my sun dial is also solar powered but doesn't need a radio reference.
12:59 AM or PM?
by
nicholaides
·
· Score: 3, Informative
Actually, if they RTFA it's 11:59 PM... just wanted to clarify.
-- http://ablegray.com
Re:Two questions
by
Mudd+Guy
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· Score: 5, Informative
Actually, it's not calculable farther in advance. The Earth's rotation is inconsistent enough that leap seconds are sometimes needed, but the need can't be predicted more than about a year in advance [1]. In other words, there is noise in the Earth's rotation period of about 1 second per year. Atomic clocks are a lot better than this (good to ~50 ns per year [2]!!!), so it's pretty easy to detect the problem.
Re:A standardized second.
by
J'raxis
·
· Score: 2, Informative
All it means is that someone looked at the conventional length of a second (1/86400 of a day) and found a natural phenomena that was really, really, really, really, really close, and unlike the length of a day, won't change over time.
As another example, take the metre. You can see how the definition of the metre became more and more precise here. I don't see it mentioned there, but the original "meaningful" definition of the metre, if extremely imprecise, is based on water: 1 ml of water = 1 gm in mass = 1 cm on each side when formed intoa cube.
According to a link I just read, POSIX doesn't handle leap seconds. So yes, if you use NTP, like someone else suggested, your time will be correct, but any measurements of time crossing leap seconds won't.
The correct solution in my opinion would be to store leap seconds along with the timezone information. That's really what they are. Unix time could be stored in TAI instead of UTC, and thus subtracting two times from each other would still give the correct result.
Whenever a leap second was announced you'd have to download a new timezone file, and if you didn't download the file in time your displayed time would be off by a second. Alternatively, if you synced using NTP, which is in UTC, and you didn't update your timezone file, then your computer would incorrectly slow down the clock by one second. Once you installed the timezone file, and resynced with NTP, this would be corrected.
Eventually NTP should probably be switched over to TAI. I see a proposal for this in a mailing list in January 2004. Would have been nice to do it before the leap second, but that's probably too soon to expect many people to change at this point.
Re:Shouldn't that be...
by
pmc
·
· Score: 2, Informative
Arrrrhhh! No.
0h 0m 0s = Midnight 12h 0m 0s = Noon.
These is no such time as 12:00:00am (or 12:00:00pm).
Slashdot Mirror
A positive leap second will be introduced at the end of December 2005.
The sequence of dates of the UTC second markers will be:
2005 December 31, 23h 59m 59s
2005 December 31, 23h 59m 60s
2006 January 1, 0h 0m 0s
Actually, its 12:00:00 then another 12:00:00.
"Martha Stewart can lick my Scrotum......do i have a scrotum?" -- Sharon Osbourne
hah, my sun dial is also solar powered but doesn't need a radio reference.
Actually, if they RTFA it's 11:59 PM... just wanted to clarify.
http://ablegray.com
Actually, it's not calculable farther in advance. The Earth's rotation is inconsistent enough that leap seconds are sometimes needed, but the need can't be predicted more than about a year in advance [1]. In other words, there is noise in the Earth's rotation period of about 1 second per year. Atomic clocks are a lot better than this (good to ~50 ns per year [2]!!!), so it's pretty easy to detect the problem.
Sorry, I can't help with the second question.
[1] See this Wikipedia article.
[2] See this Wikipedia figure.
I just wanted to be the first to mention this site, someone wanted to view the previous leap second, and that became an obsession.
Okay, here's a clickable link:
http://leapsecond.com/
An obsession in another are of time is this Y10K Compliant clock:
http://longnow.org/
Tag lost or not installed.
As another example, take the metre. You can see how the definition of the metre became more and more precise here. I don't see it mentioned there, but the original "meaningful" definition of the metre, if extremely imprecise, is based on water: 1 ml of water = 1 gm in mass = 1 cm on each side when formed intoa cube.
Liberty in your lifetime
According to a link I just read, POSIX doesn't handle leap seconds. So yes, if you use NTP, like someone else suggested, your time will be correct, but any measurements of time crossing leap seconds won't.
The correct solution in my opinion would be to store leap seconds along with the timezone information. That's really what they are. Unix time could be stored in TAI instead of UTC, and thus subtracting two times from each other would still give the correct result.
Whenever a leap second was announced you'd have to download a new timezone file, and if you didn't download the file in time your displayed time would be off by a second. Alternatively, if you synced using NTP, which is in UTC, and you didn't update your timezone file, then your computer would incorrectly slow down the clock by one second. Once you installed the timezone file, and resynced with NTP, this would be corrected.
Eventually NTP should probably be switched over to TAI. I see a proposal for this in a mailing list in January 2004. Would have been nice to do it before the leap second, but that's probably too soon to expect many people to change at this point.
Arrrrhhh! No.
0h 0m 0s = Midnight
12h 0m 0s = Noon.
These is no such time as 12:00:00am (or 12:00:00pm).
See NIST for the gory details.