[LEAPSECS] ACM article

[Rob Seaman]

Hi Tom,


> Help me out here. That ACM generated time-stamp in your posting; which is it by your definition: time-of-day or interval timekeeping?


Universal time is time-of-day.  The current definition of UTC permits it to be used to recover an interval timescale.  Timestamps supply information about both time-of-day and an interval since an epoch.  More to the point the interval may be in evenly-tempered units or in jerked-about-by-the-moon units.  It may very well be of interest to different stakeholders whether the stamped event occurred at "noon" or rather whether it occurred so many thousands or millions of SI seconds before or after some other event.  The current definition of UTC preserves access to both.

In a more coherent world, interval times would always be expressed as an unending count of seconds since some epoch; sexagesimal would be reserved for the repeating quantity of angles like time-of-day.  In a more coherent world, the unit of interval time would not have been chosen to spoof an angle such as 1/60 of 1/60 of 1/24 of a mean solar day.

The issue is that if the ITU wishes to rearrange things to more generally confuse interval timekeeping with time-of-day - thereby ejecting Earth orientation from the system - that this places requirements on their planning process to handle the edge cases.  They are rather seeking to bury the edge cases.

On this list we have covered vast numbers of possible ways to address the various requirements.  The ITU wishes to pretend that the engineering requirements do not exist.  PHK wishes to pretend that requirements deemed "sexy" by the ACM trump all others.  I predict that should the ITU succeed in their woebegone quest to bastardize the definition of Universal Time generally, and UTC in particular, that those hidden requirements will pop out unexpectedly in the most "entertaining" ways for decades to come.

This list is called "leapsecs".  This doesn't mean that leap seconds are the beginning and ending of the underlying issues.  Civil timekeeping is layered on the synodic day. Leap seconds are merely a way to satisfy that requirement.  Getting rid of leap seconds doesn't get rid of the requirement.

Rob