Extra Leap Second To Be Added To Clocks On June 30
"On June 30 this year, the day will last a tad longer — one second longer, to be precise — as a leap second is to be added to clocks worldwide. The time UTC will go from 23:59:59 to 23:59:60 in order to cope with Earth's rotation slowing down a bit. So, what do you intend to do during that extra second added to that day? Well, you may want to fix your systems. The last time a leap second was added, in 2012, a number of websites, Java and even Linux experienced some troubles. Leap seconds can be disruptive to precision systems used for navigation and communication. Is there a better way of dealing with the need for leap seconds?" -- source: http://news.slashdot.org/story/15/01/06/1821234 Cheers, Peter -- Peter Reutemann, Dept. of Computer Science, University of Waikato, NZ http://www.cms.waikato.ac.nz/~fracpete/ Ph. +64 (7) 858-5174
On Wed, 7 Jan 2015 10:22:31 +1300, Peter Reutemann wrote:
"... Is there a better way of dealing with the need for leap seconds?"
Some suggest getting rid of them altogether, which means official timekeeping will no longer stay in sync with the Earth’s rotation. Most of our date/time routines can’t cope with them.
Interesting that the leap day at end of Feb every 4 years is not an issue but the leap second is? Seems arbitrary that one time unit proves problematic but another doesn't. On Wed, 2015-01-07 at 11:45 +1300, Lawrence D'Oliveiro wrote:
On Wed, 7 Jan 2015 10:22:31 +1300, Peter Reutemann wrote:
"... Is there a better way of dealing with the need for leap seconds?"
Some suggest getting rid of them altogether, which means official timekeeping will no longer stay in sync with the Earth’s rotation.
Most of our date/time routines can’t cope with them. _______________________________________________ wlug mailing list | wlug(a)list.waikato.ac.nz Unsubscribe: http://list.waikato.ac.nz/mailman/listinfo/wlug
On Wed, Jan 07, 2015 at 02:50:21PM +1300, GJB wrote:
Interesting that the leap day at end of Feb every 4 years is not an issue but the leap second is? Seems arbitrary that one time unit proves problematic but another doesn't.
It is unusual for software with dates not to program the extra day in February for leap years as it is a straightforward calculation to determine when it applies, whereas much software cannot cope with 61s in a minute despite the C library standard functions explicitly stating that valid values for the seconds field (in broken down time) include 60. A further complication is that the tzdata must be up to date for the C library to be able to convert from Unix time (a single integer for the number of seconds since the epoch) to a time zone, that is, the C library must be told about the presence of the leap second as it cannot be algorithmically predicted. If the tzdata have not been recently updated it is quite possible that a system will not know about the leap second and thus convert times subsequent to the leap second incorrectly. Cheers Michael.
On Wed, 7 Jan 2015 15:06:35 +1300, Michael Cree wrote:
A further complication is that the tzdata must be up to date for the C library to be able to convert from Unix time (a single integer for the number of seconds since the epoch) to a time zone
Which is why I really, really like software that refers to the standard copy of tzdata in /usr/share/zoneinfo, rather than maintaining its own copy. tzdata gets updated several times a year, and it shouldn’t require software patches to umpteen different packages to keep this current. Remember all the hassles with Windows a few years ago when both the US and NZ extended their daylight-saving periods? And then in 2010, Paraguay changed its daylight-saving rule with less than a month’s notice. The tzdata maintainers had a patch within just a few days.
On Wed, Jan 07, 2015 at 04:02:38PM +1300, Lawrence D'Oliveiro wrote:
On Wed, 7 Jan 2015 15:06:35 +1300, Michael Cree wrote:
A further complication is that the tzdata must be up to date for the C library to be able to convert from Unix time (a single integer for the number of seconds since the epoch) to a time zone
Which is why I really, really like software that refers to the standard copy of tzdata in /usr/share/zoneinfo, rather than maintaining its own copy.
Absolutely! I get annoyed with libical which has its own time zone data and for NZ does not have historical DST info...
Remember all the hassles with Windows a few years ago when both the US and NZ extended their daylight-saving periods?
Not just Windows, but Apple who did not issue an update for Mac OS X until some weeks after the NZ daylight saving change and recommended on their forum that NZers just adjust the system clock by one hour for the week or two that it displayed the wrong times, without warning that certain entries one put into the Calendar program (and elsewhere) would end up in the wrong hour when one corrected the clock back. In contrast Linux distributions had updates for tzdata well in time for the NZ DST change. Cheers Michael.
On Wed, 7 Jan 2015 17:17:18 +1300, Michael Cree wrote:
On Wed, Jan 07, 2015 at 04:02:38PM +1300, Lawrence D'Oliveiro wrote:
Remember all the hassles with Windows a few years ago when both the US and NZ extended their daylight-saving periods?
Not just Windows, but Apple who did not issue an update for Mac OS X until some weeks after the NZ daylight saving change and recommended on their forum that NZers just adjust the system clock by one hour for the week or two that it displayed the wrong times, without warning that certain entries one put into the Calendar program (and elsewhere) would end up in the wrong hour when one corrected the clock back. In contrast Linux distributions had updates for tzdata well in time for the NZ DST change.
Does OS X set the system clock in local time rather than UTC? Because, fiddling UTC time just to compensate for a wrong local-time offset is not a good idea.
On Wed, 07 Jan 2015 14:50:21 +1300, GJB wrote:
Interesting that the leap day at end of Feb every 4 years is not an issue but the leap second is? Seems arbitrary that one time unit proves problematic but another doesn't.
Don’t let the “leap” name confuse you: the two are quite different things. The extra day during leap years is included according to a predictable rule, but leap seconds are added (or potentially subtracted, but this has never happened) depending on how the rotation of the Earth slows down or speeds up, which follows no fixed rule.
By the way, coolest name for an outfit to work for: “Earth Rotation Service”. Though it seems their official name is now “International Earth Rotation and Reference Systems Service” <http://www.iers.org/IERS/EN/Home/home_node.html>.
participants (4)
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GJB -
Lawrence D'Oliveiro -
Michael Cree -
Peter Reutemann