Leap second tonight

Marshall Eubanks tme at multicasttech.com
Mon Jan 5 17:21:22 UTC 2009

On Jan 5, 2009, at 11:30 AM, Adrian Chadd wrote:

> This begs the question - how the heck do timekeepers and politicians  
> get
> away with last minute time changes?
> Surely there's -some- pushback from technology related interest  
> groups to
> try and get more than four weeks warning? :)

Having been involved in the leap second business, I can tell you that  
Gambis strictly follows the rules, which are
Bulletin C is mailed every six months, either to announce a time step  
in UTC or to confirm that there will be no time step at the next  
possible date.
If you want more lead time warning, pay attention to the LOD graph in


The long term LOD offset is about 1 msec now. That means that every  
day, Earth time and atomic time will drift off by 1 msec. Since there
are 1000 msec in the second, and since the rule is that a leap second  
is chosen when the difference (UT1−UTC) approaches 0.9 seconds,  
out to the next period, and since the strong preference is to have  
leap seconds in January, you can generally figure out what will happen  
Daniel announces it.

For example, in one year the offset should be ~ 400 msec, so I will  
informally predict another leap second in January, 2011, not 2010.
Keep watching that graph.

Anyone who is dealing with Leap Second code should keep in mind that  
negative leap seconds (i.e., no second # 59, instead of an extra  
second called
60) are a distinct possibility. It all depends on the "weather" at the  
core mantle boundary - note that the LOD offset was almost 3 msec not  
too long ago.


> Adrian
> On Mon, Jan 05, 2009, Frank Bulk wrote:
>> A report from a DHCP/DNS appliance vendor here:
>> ====================
>> Several customers have reported a complete lock-up of their Proteus  
>> system
>> around the beginning of January 1st 2009. We believe that we have  
>> traced
>> this to a problem in the underlying kernel and NTP and the handling  
>> of the
>> date change associated with 2008 being a Leap Year and therefore  
>> having 366
>> days.
>> Several conditions must be met to trigger this problem:
>> 1. The Proteus was originally installed as v2.1.x or earlier.
>> 2. NTP is enabled as a client with 2 or more external source servers
>> defined.
>> 3. There is a discrepancy in the times reported back by these other  
>> NTP
>> servers.
>> There is no correction available at this time, and the resolution  
>> is to
>> power cycle the system, after which it will run fine.
>> If you experienced a similar problem at the indicated time, please  
>> submit a
>> trouble ticket so that we can confirm that this occurred on your  
>> system.
>> ====================
>> I don't know what the underlying OS is.
>> Frank
>> -----Original Message-----
>> From: Kevin Day [mailto:toasty at dragondata.com]
>> Sent: Wednesday, December 31, 2008 4:42 PM
>> To: NANOG list
>> Subject: Leap second tonight
>> Just a reminder that there's a leap second tonight.
>> Last time I watched for what happened on 01/01/2006, there was a
>> little bit of chaos:
>> http://markmail.org/message/cpoj3jw5onzhhjkr?q=%22kevin+day%22+leap+second+r
>> eminder+nanog&page=1&refer=cnkxb3iv7sls5axu
>> I've been told that some of the causes of these problems are fixed on
>> any reasonably recent ntp distribution, but just in case, you might
>> wanna keep an eye out if you're seeing any weirdness. The worst  
>> damage
>> I'd heard from anyone after that event was their clock being
>> significantly off for several hours.
>> -- Kevin
> -- 
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