Re: [art] summary of updates - draft-time-touch

[Michael Thornburgh <[e-mail]>]

Joe, all.

i have several problems with this draft.  as others have mentioned, i think it's too long and complicated.  also, i feel that several of the definitions in section 3 Terminology are inaccurate or imprecise.

below are my proposals for some of the Terms:

 o Instant: a point in time.

 o Time scale: the assignment of names to points in time.

 o Date: the name of an instant in a time scale.  alternatively: the name of a day in a calendar.

 o Unit of time: this is unnecessary

 o Epoch: a point in time that is the anchor/origin/beginning of a time scale.

 o Clock: an apparatus that measures (and typically reports) the passage of time.  a clock may report the time according to a time scale.

 o Solar day: TL;DR.  please make more concise.  "mean solar day" would be useful to UT1 and therefore UTC.

 o Tropical year: TL;DR.  is this necessary if you have "mean solar day"?

 o Second: the basic unit of time, having multiple different definitions:

   * 1/86400 of a day / mean solar day.

   * SI second: 9192631770 periods of the radiation corresponding to the hyperfine transition of the ground state of cesium 133 at 0K.  (note that sea level is NOT part of the definition of the SI second)

 o Leap second: an extra second irregularly inserted into or removed from the Coordinated Universal Time time scale to keep it within 0.9 seconds of UT1.

 o Leap day: this is unnecessary.

section 4.2 Time scales: 

 o TAI (International Atomic Time): an ensemble coordinate time scale based on the SI second at mean sea level ("on the geoid"), determined after-the-fact by the weighted contributions of numerous atomic clocks in laboratories around the world, adjusted to account for gravitational time dilation caused by the altitude of each clock (among other gravitational effects).  TAI may appear to tick faster or slower than the SI second depending on the location (especially altitude) of the observer; therefore, free-running atomic clocks may diverge from TAI.  only approximations of TAI are available in real-time.

i think it's important to make the above points about TAI because it illustrates why having an atomic clock on your desk or in your computer isn't good enough.

 o UTC (Coordinated Universal Time): an approximation of UT1 based on TAI *adjusted* with leap seconds.

later, in section 5, there is the implication that UTC is discontinuous.  UTC is continuous and ticks at the same rate as TAI.  leap seconds are not discontinuities.  the counting is non-uniform in that occasionally and irregularly there are minutes that don't have the *usual* number of seconds in them.

POSIX time has discontinuities because it is fundamentally flawed.

there are other problems with the document, but i think dealing with them will be easier once the issues above are addressed.

-mike

________________________________________
From: art [[e-mail]] on behalf of Joe Touch [[e-mail]]
Sent: Monday, April 17, 2017 2:32 PM
To: [e-mail]
Subject: Re: [art] summary of updates - draft-time-touch

Hi, all,

I've completed an update that rolls in the changes below as well as a
few other issues raised off-list.

Joe

A new version of I-D, draft-touch-time-02.txt
has been successfully submitted by Joe Touch and posted to the
IETF repository.

Name:           draft-touch-time
Revision:       02
Title:          Resolving Multiple Time Scales in the Internet
Document date:  2017-04-17
Group:          Individual Submission
Pages:          17
URL:            [mangled URL removed]
Status:         [mangled URL removed]
Htmlized:       [mangled URL removed]
Htmlized:       [mangled URL removed]
Diff:           [mangled URL removed]

Abstract:
   Internet systems use a variety of time scales, which can complicate
   time comparisons and calculations. This document explains these
   various ways of indicating time and explains how they can be used
   together safely. This document is intended as a companion to
   Internet time as discussed in RFC 3339.