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Re: Leap second tonight
From: Marshall Eubanks <tme () multicasttech com>
Date: Mon, 5 Jan 2009 12:21:22 -0500

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 Daniel
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, projected 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 before
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.



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

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
3. There is a discrepancy in the times reported back by these other NTP

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.


-----Original Message-----
From: Kevin Day [mailto:toasty () 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:

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

- Xenion - http://www.xenion.com.au/ - VPS Hosting - Commercial Squid Support - - $25/pm entry-level VPSes w/ capped bandwidth charges available in WA -

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