[tz] Future support for more reliable pre-1970 data

[Alan Barrett]

On Fri, 20 Sep 2013, Lester Caine wrote:
> Subject: Re: [tz] What is LMTZ?

Please change the Subject when you change the topic.

> I think we have reached the point where it's clear that TZ 
> is never going to support anything before 1970 with any 
> reliability.

That's not at all clear to me, at least for values of "reliable" 
that approximate the best information that volunteers are able to 
find and contribute.

I thought that we had been talking about ways to allow the tz 
project to add much more pre-1970 data without adversely affecting 
those who don't want the run time overhead of the additional data, 
and that winnowing support would be one of the first steps towards 
that future.

> winnowing is a pointless exercise unless you are prepared to add 
> new data later.

Well, yes.  The reason we have been talking about winnowing is 
that it will allow new data to be added later

> So the only SAFE way to distribute a sub-set of TZ data is not 
> to link it to past history that it is not 100% related to. The 
> only problem remaining is how to allow a correct historic record 
> to be used with the restricted TZ data.

I can't parse that, but I suspect that it's a conclusion based on 
a premise that I don't accept.

--apb (Alan Barrett)