[LEAPSECS] honest-to-god copper

Rob Seaman seaman at noao.edu
Mon Jun 7 14:25:03 EDT 2010

So they are asserting that TimeScaleInstant conforms to (some
realization of) the actual UTC? Is this assertion correct? Why then
prefer the just plain (and incorrect) Instant class?

Stating that not taking into account leap seconds is useful because
"most applications do not take into account the existence of leap
seconds" is a rather circular justification.

Many applications (don't know about "most") have civil timekeeping
requirements. Civil timekeeping is layered on UTC, which requires
leap seconds. Thus many (or most) applications require leap seconds,
whether the programmers and project management want to admit it or not.

Most applications require arithmetic. One could define an "Addition"
class in which 1+1 is 3. And a "TrueAddition" class in which 1+1 is 2
for "applications needing to take into account the way arithmetic
actually works". Reifying an object to a nonsensical class is not
made a logically coherent action just because you've checked your code
into a source repository and written documentation with disclaimers.


On Jun 7, 2010, at 10:34 AM, Steve Allen wrote:

> In the Manhattan project plutonium was copper, and copper was

> honest-to-god copper.


> In the Java JSR-310 "Date and Time API"

> https://jsr-310.dev.java.net/userguide.html

> we see this:


> Time scales


> The Instant class operates on a time-line model that doesn't

> exist in reality. Specifically it assumes that leap-seconds

> do not exist, and that there are always 60 seconds in a

> minute.


> These simplifications are useful because most applications do

> not take into account the existence of leap seconds. If your

> application needs to takeinto account leap seconds then an

> alternate class is needed. The TimeScaleInstant class

> represents an instant in time measured againsta specific

> TimeScale. The supplied scales include TAI and True-UTC.


> "True-UTC", as opposed to just plain "UTC". Just plain "UTC" is not

> the entity defined by ITU-R TF.460, but a (dare I use the word)

> proliferated time scale, something new created by them.


> How long will it be before it is necessary to make the distinction

> between "TAI" in JSR-310 and "True-TAI" as defined by BIPM?


> I think I would call this not "proliferation" but "dilution of

> trademark".


> Who is in charge of these time scales?

> The defining agencies and their documents, or various different sets

> of time scale users and their documents?


> --

> Steve Allen <sla at ucolick.org> WGS-84

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