[LEAPSECS] Consensus building?

Stephen Colebourne scolebourne at joda.org
Wed Feb 2 13:44:42 EST 2011

On 2 February 2011 18:13, Warner Losh <imp at bsdimp.com> wrote:

>> - an SI-based-minute is formed from exactly 60 SI-seconds

>> - an SI-based-hour is formed from exactly 60 SI-based-minutes and thus

>> exactly 3600 SI-seconds

>> - an SI-based-day is formed from exactly 24 SI-based-hours and thus

>> exactly 86400 SI-seconds


> These are true only most of the time.  On leap second day, they are all

> false and off by 1, typically one low.  It all depends on the timescale that

> you use, and thus there can't be a universal definition here.

You're reading more into the statement than is intended by trying to
interpret them as a time-scale or clock. I'm defining a unit of
SI-based-minute that is a multiple of 60 of the unit SI-second. No
more no less.

>> Solar

>> - a solar-day is a measured period of time

>> - the length of a solar day in in SI-seconds varies over time

>> - the length of a solar day in in SI-seconds is on average increasing with

>> time

>> - a solar day is not a fixed number of SI-seconds

>> - a solar-hour is the period of 1/24th of a single measured solar-day

>> - a solar-minute is the period of 1/60th of a solar-hour and thus

>> 1/1440th of a single measured solar-day

>> - a solar-second is the period of 1/60th of a solar-minute and thus

>> 1/86400th of a single measured solar-day


> Except that the last bits are wrong here too.  It isn't the measured solar

> day, except for UT, but the average of the measured day smoothed in

> different ways for UT1 and UT2.


> Also, implicit in this definition is the astronomical term solar-day, so

> your definition is circular.  A solar day is the amount of time it takes the

> earth to rotate until the sun is in the same apparent position in the sky,

> as opposed to a sidereal day, which is 360 degrees of rotation.

So why not tweak these, or try to build consensus around a different
set of statements?

>> UTC-2011

>> - the UTC-2011 time-scale is known as UTC in the year 2011

>> - the UTC-2011 time-scale is a continuous count of SI-seconds

>> - the UTC-2011 time-scale defines UTC-2011-days

>> - a UTC-2011-day is either 86400 SI-seconds or 86401 SI-seconds long

>> - the additional SI-second in a UTC-2011-day is a leap-second

>> - the presence or absence of a leap-second is determined up to 6

>> months in advance


> yes.  This time Bulletin came out this morning, giving only 5 months of

> notice of no leap second.


> I'm also not sure that this notation is the best.  We're really using

> UTC-1972 right now, if we follow the convention of using the year of the

> last change.  We'd also be on TAI-2008 based on the last time the averaging

> algorithm of TAI was changed.

We should use UTC-1972 as a terminology if has broader agreement.


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