# [ntp:questions] The Leap Millisecond

Guy Macon "http://www.guymacon.com/" at ntp.isc.org
Sun Jun 3 13:30:32 UTC 2007

```

(While researching this, I came across the leap second list
at [ http://www.ee.udel.edu/~mills/leap-seconds.3169152000 ],
which expired in 2004.  Does anyone know of a newer version?)

In the sci.astro.amateur and sci.astro newsgroups (See "Avoiding

>I've come up with an alternate scheme.
>
>Divide the year into ten parts of 37 and 36 days in alternation. Start
>from March 1 to keep things simple in leap years.
>
>For the first 33 1/3 days of each of those parts, sweep increments of
>100 milliseconds "under the rug" by adding one millisecond to the last
>second of each eight-hour period. This would allow a time scale to be
>kept within 0.1 seconds of mean solar time, and it would also mean
>that, most of the time, a time signal would consist of a steady stream
>of SI seconds; the long seconds would come at predictable intervals.

An excellent scheme.  Let me be the first to say that I approve.

Looking forward to possible objections to certain seconds being
1.001 times longer or shorter than most of the other seconds,
that seems to me to be far less troublesome than having some
minutes be some 1.01666... times longer or shorter than most
of the other minutes using leap seconds.

The above scheme and the existing leap second scheme both
result in the exact same length of the millisecond, microsecond,
nanosecond, etc.  Those are much more commonly used than the
second is in the areas of physics and engineering.  In the area
of computers, time is typically specified as date and time, which
means that the computers already have to work with the occasional
minute that is 59 or 61 seconds long.

The above scheme results in a length for the minute, hour and day
that is no more than a millisecond larger or smaller than  most of
the other minutes, hours or days.  This is a thousand times closer
than under the leap second scheme.  Months and years would be ten
times closer.

References:

The NTP Timescale and Leap Seconds:
http://www.ee.udel.edu/~mills/leap.html
(also touches on GPS)

The Future of Leap Seconds
http://www.ucolick.org/~sla/leapsecs/onlinebib.html

Propagation of a leap second
http://members.iinet.net.au/~nathanael/ntpd/leap-second.html

Leap Second Mailing List:
http://rom.usno.navy.mil/archives/leapsecs.html

--
Guy Macon
<http://www.guymacon.com/>

```