[tz] Regression Tests and Revision Controls

Lester Caine lester at lsces.co.uk
Tue Aug 12 09:45:33 UTC 2014

On 11/08/14 09:39, Lester Caine wrote:
> My own Hg DVCS view allows
> me to step through the history of file changes so Ican check this
> manually but I'm back to the point I was at several years ago where I
> want the data in a relational database with a version tag, and all I
> need to add IS the diff's each release ...

OK I have been looking at this from the wrong end. Basically what I'm
trying to flag up is when data that has already been normalized needs to
be reviewed because of a change in tz. I'd been looking at historic
data, but as Paul says ... future offsets are a guess already, and so
it's this area I need to be targeting. The historic changes just come
out in the wash. This may actually be a discussion that should be on the
tzdist list, so I have copied there as well.

That we need to know which version of tz was used to normalize a record
has been a given, so when an update occurs we can identify which time
zone has been updated and where in time the change happened. As a
minimum flagging an historic record where it is identified with a tz
version that has a change from the current version when it is used.

We have been trying to get to a point where the historic tz data is
stable and acceptable to everyone. From a tzdist point of view, I would
contest that having proven historic data prior to 1970 is essential as
not including it leaves a hole in how useful the information is. I
presume that the tzdist discussion is based on prompt updates to data
going forward, but would not exclude corrections to the historic
material as well? Either way, picking up when stored information has
changed is important?

Having the information that there has been a change is one thing, using
it is something else.

Lester Caine - G8HFL
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