IERS ponders reverse leapsecond...

Marshall Eubanks marshall.eubanks at
Wed Aug 3 15:47:52 UTC 2022

Just to set the standard.

There is no "during" a negative leap second.

A positive leap second proceeds as
23:59:60 <--- second added here

A negative leap second proceeds as
00:00:00 <--- whoops! second 59 is gone!!!

Those systems that "smear" leap seconds over a 24 hour period will
presumably just smear in the reverse direction.

It would not surprise me at all if the liquid outer core keeps on its
slowdown and a negative leap second would need to be scheduled sooner
or later.

Marshall Eubanks

On Wed, Aug 3, 2022 at 11:35 AM Matthew Huff <mhuff at> wrote:
> True,
> But it's hard enough to get developers to understand the need to code for 61 seconds in a minute, and now they would need to code for 59 seconds as well.
> If time systems simply skewed the time so that 60 seconds actually just took 61 seconds or 59 seconds, there would be other issues, but coders wouldn't be involved.
> -----Original Message-----
> From: NANOG < at> On Behalf Of Stephane Bortzmeyer
> Sent: Wednesday, August 3, 2022 11:19 AM
> To: Jay Ashworth <jra at>
> Cc: nanog at
> Subject: Re: IERS ponders reverse leapsecond...
> On Wed, Aug 03, 2022 at 11:09:25AM -0400,  Jay Ashworth <jra at> wrote  a message of 32 lines which said:
> > General press loses its *mind*:
> Indeed, they seem not to know what they write about. "atomic time – the universal way time is measured on Earth – may have to change" They don't even know the difference between TAI and UTC.

More information about the NANOG mailing list