[LEAPSECS] presentations from AAS Future of Time sessions

[Magnus Danielson]

On 06/01/14 19:40, Rob Seaman wrote:

> PDFs of the slides from the talks yesterday (5 Jan 2014) are now available at:

>

> 	http://www.cacr.caltech.edu/futureofutc/aas223/


Thanks for the pointer.

Reviewing Kara Warburton's presentation I have one comment.
The concept of a international time-scale with no leap-second isn't a 
new concept. It already exists even if it's use have been discouraged. 
It's called TAI. TAI, or shifted versions of TAI such as the GPS 
time-scale, is already being used when a no-leapsecond base is needed.

When UTC needs to be realized, providing a side-channel holding 
leap-second could and when new leapseconds is going to be introduced is 
being built, and is well understood how it needs to work from the 
existing standard, and it works.

Using TAI instead of UTC in the POSIX time_t engine works out of the 
box, but causes greif when UTC is required, as POSIX has no defined 
side-channel for handling the TAI-UTC difference. Adding such a 
side-channel interface to be optionally included for those needing the 
actual UTC and used by applications where using actual UTC is needed 
will be the fix to POSIX that is a result of not including leap-seconds 
properly into time_t. The side-channel is needed even if retaining the 
current UTC to time_t mapping.

Creating a new leap-second free time-scale would just add to the 
proliferation of TAI variants, and the proposed name is trying to be a 
TAI variant. It would be more straightforward to accept that there needs 
to be two international time concepts, with and without leap-seconds. 
Those concept exists in UTC and TAI respectively. Let's use them that way.

Cheers,
Magnus