[time-nuts] Leap Quirks

Chuck Harris cfharris at erols.com
Sun Jan 4 09:57:01 EST 2009


Poul-Henning Kamp wrote:
> In message <4960027E.1000103 at erols.com>, Chuck Harris writes:
>> Poul-Henning Kamp wrote:
> 
>>>> Ok, that is news to me.  Are you saying that (pulling a number out of
>>>> the air) time_t = 21120123 could be followed by 21120123 on a year where
>>>> we added a leap second?
>>> Apart from the number, that is exactly what happens: The last
>>> second of the (UTC) day is recycled twice.
>> [...] and all of the sources I have found
>> concur that time_t is the number of seconds since 1/1/1970 UTC without
>> regard to leap seconds.
>>
>> When did this change?
> 
> Never, that's the trouble.
> 
> time_t is better defined as:
> 
> 	d * 86400 + min(rs, 86399)
> 
> where:
> 	d = Number of complete days since 1970-01-01H00:00:00Z 
> 	rs = number of seconds since UTC midnight.
> 
> Eliminating leapseconds would make it correct however.

Language is such a problem with these discussions.  Your equation
says exactly what I believe to be true, but your use of the word
correct muddles everything for me.  POSIXly correct, and unixly
correct is when time_t follows your equation.  Following UTC is
another kind of correct: politically correct.

I believe your use of the phrase "make it correct" shows your bias
towards removing the leap second corrections from UTC.  This is my
bias as well.

-Chuck Harris




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