[tz] Fractional seconds in zic input

John Hawkinson jhawk at MIT.EDU
Tue Feb 6 03:31:56 UTC 2018

Paul Eggert <eggert at cs.ucla.edu> wrote on Mon,  5 Feb 2018
at 09:23:04 -0800 in <c968840d-014f-abdf-8efa-778c297039fc at cs.ucla.edu>:

> Although it doesn't add value for today's timestamps, it is useful
> for historical timestamps that have been covered by the database for
> decades. Some applications do deal with older timestamps, and when
> it's easy (as it is here) it's helpful to correct longstanding data
> entry errors that were forced by an inadequate format.

I question this claim, that it is helpful to correct longstanding data entry errors. The result is that historical timestamps in such zones change, and interval times that may have been previously calculated may change, either becoming incorrect (or correct; or "differntly incorrect").

Those are not necessarily minor changes.

We should pause before "correcting" historical timestamps, even if we think the change is better. (In practice, I suppose, we have been making changes willy-nilly to historical timestamps for long enough that anyone who cares has likely already been burned by it and adopted a solution to mitigate it, although what that looks like I am not sure. I'm not sure this is a great argument to keep doing so...) 

--jhawk at mit.edu
  John Hawkinson

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