[tz] Stability versus correctness

Alan Barrett apb at cequrux.com
Fri Jul 11 07:04:04 UTC 2014

On Thu, 10 Jul 2014, Paul Eggert wrote:
>I doubt whether there's a genuine lack of concern about accuracy or 
>correctness.  On the contrary, I think we all want the data to be as 
>accurate and correct as it can be.  The only dispute here is how much 
>stability trumps these other concerns.

Here's where I'd draw the line:  If we obtain new information 
with higher assurance than the old information (or guesses), then 
we should update the database with the new information, for the 
sake of accuracy.  If we believe that the old information has low 
assurance, but we do not have higher assurance information to 
replace it, then we should leave the old information in place, for 
the sake of stability.

For example, if you believe that the date that a zone switched 
from LMT to a standard time with a "round number" offset from UT 
is just a guess with low assurance, then leave it alone, until 
better information becomes available; don't link the zone to 
another zone that was similar but had a different "guess" for the 
data of the switch from LMT to a standard time.  If you learn 
better information, then adjust the database accordingly.

--apb (Alan Barrett)

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