[LEAPSECS] internet drafts about zoneinfo

[Joe Gwinn]

At 1:03 PM +0000 3/7/11, Tony Finch wrote:

>On Sun, 6 Mar 2011, Joe Gwinn wrote:

>>

>>  So, we have an instant in time that is forever fixed,

>

>Yes.

>

>>  and a progress rule that counts out uniform seconds (ideally SI seconds

>>  the standard says in the Rationale).

>

>No. POSIX time does not define a progress rule. It is defined by a formula

>that maps UTC time labels into a flat counter.


Yes, POSIX does have a progress rule.  It adds one second per SI 
second to the Seconds Since the Epoch counter, and converts this 
count to something resembling UTC (but having no leap seconds).  It 
may be ugly, but it is still a progress rule.



>  > The actual requirement is "As represented in seconds since the Epoch,

>>  each and every day shall be accounted for by exactly 86400 seconds."

>

>That is a rephrasing of part of the defining formula. The preceding

>sentence is "How any changes to the value of seconds since the Epoch

>are made to align to a desired relationship with the current actual

>time is implementation-defined." What the two together mean is that the

>counter goes up by 86400 per day regardless of any adjustments to align

>the clock with "actual time" (whatever that means).


I don't know what "actual time" means either, but I do know the 
context - a time war had broken out, and most of the committee fled 
for the hills.  Time is not very high on their agenda.



>  > > What has been said many times is that it might be nice to 

>change POSIX time

>>  > to be based on TAI but if you try it you find that this breaks most

>>  > timekeeping code.

>>

>>  Why?

>

>Because the code assumes that the formula in section 4.15 gives the

>relationship between UTC and posix time.


No it doesn't.  See above.  By the way, I wrote goodly parts of this 
part of the standard, so I do have some idea of the intent, however 
misguided it may be.


Joe Gwinn




>Tony.

>--

>f.anthony.n.finch  <dot at dotat.at>  http://dotat.at/

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