[LEAPSECS] Admins should check expiration date of leap second file

Martin Burnicki martin.burnicki at meinberg.de
Mon Dec 21 08:32:21 EST 2015


I've just checked some of the commonly known sources for the leap second
file to be used with NTP and found that some sites on the internet only
provide outdated versions of the leap second file. Some of the files
will expire on 28 December 2015.

So if you have an NTP daemon running and a leap second file specified in
the ntp.conf file you should check if you have a current copy of the
file installed, or otherwise update the leap second file.

Unlike earlier version of ntpd (up to 4.2.6*), current versions (4.2.8*)
of the NTP daemon really evaluate the expiration date of the file, and
don't accept outdated an outdated leap second file.

For many NTP installations this doesn't really matter, but

- if an applications expects a current TAI offset set in the OS kernel
then it won't get the correct information without a valid leap second file

- if a valid leap second file is available then the leap second
information takes precedence over leap second announcements from
upstream servers, etc., so a valid leap second files provides some
protection against wrong leap second announcements from faulty upstream

The original leap second file from NIST is available via this link:
ftp://time.nist.gov/pub/leap-seconds.3629404800 (current)
ftp://time.nist.gov/pub/leap-seconds.list (link to current)

and the current version expires 28 June 2016. However, unfortunately the
NIST server is often not reachable.

The IERS which decides whether a leap second is to be scheduled or not,
is now also providing an own leap second file:

https://hpiers.obspm.fr/iers/bul/bulc/ntp/leap-seconds.3651350400 (current)
https://hpiers.obspm.fr/iers/bul/bulc/ntp/leap-seconds.list (link to

However, this file already expires on 28 January 2016, which is pretty
early. I've already contacted the folks at IERS and asked them to set
the expiration date to shortly before the next leap second event. I
guess they will provide a new leap second file shortly after the next
bulletin C has been published in January 2016.

The USNO formerly also provided an own version of a leap second file via

However, on this web page there is only an outdated copy of the IERS
file now, which expires on 28 December 2015. I've already tried to
contact the folks at USNO and asked them to update their server, but
haven't received a reply, yet.

A copy of the current leap second file can also be found in the current
Time Zone data package provided by the IANA. Since the IETF web site
provides an unpacked copy of the tzdata archive the NIST file is also
available here:
http://www.ietf.org/timezones/data/leap-seconds.list (shipped with
tzdata, copy of a NIST file)

Since this is a copy of the current NIST file this file is valid until
28 June 2016.

Another copy of the current NIST leap second file is available via the
Meinberg web site:

Hope this helps.

Martin Burnicki

Senior Software Engineer

MEINBERG Funkuhren GmbH & Co. KG
Email: martin.burnicki at meinberg.de
Phone: +49 (0)5281 9309-14
Fax: +49 (0)5281 9309-30

Lange Wand 9, 31812 Bad Pyrmont, Germany
Amtsgericht Hannover 17HRA 100322
Geschäftsführer/Managing Directors: Günter Meinberg, Werner Meinberg,
Andre Hartmann, Heiko Gerstung
Web: http://www.meinberg.de

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