On 12-5-2018 02:25, Lester Caine wrote:
On 12/05/18 00:32, Adriano dos Santos Fernandes wrote:
On 11/05/2018 19:48, Lester Caine wrote:
There is no information on those pages covering just what way the base
TZ data is processed. I think it is probably safe to assume that it is
unusable for providing timezone offsets prior to 1970 which is the
current target of TZ itself, so it would be nice if there was a suitable
warning somewhere? But some way to restore the pre 1970 data would be
useful!
ICU has the latest database here:
http://source.icu-project.org/repos/icu/data/trunk/tzdata/icunew/2018e/
The original one:https://www.iana.org/time-zones (2018e from
2018-05-01).
The IANA files mention back zones.
If you have more accurate data, I'm sure it would be possible to
contribute there.
I think I have had confirmation that the stock ICU distribution does not
include the backzone data, only the timezone id's that have been
stripped in the zone1970.tab list. I have contributed data which you
will see in the backzone file and which we know is correct, but instead
we get data prior to 1970 for the wrong timezone and no indication that
the data is wrong! Paul refuses to include pre-1970 data as it 'may be
incorrect', but the result is that one has to assume ALL pre-1970
offsets are incorrect instead, despite people putting a lot of work into
researching the missing pre-1970 data ...
From TZ file history
"A new file 'backzone' contains data which may appeal to
connoisseurs of old time stamps, although it is out of scope for
the tz database, is often poorly sourced, and contains some data
that is known to be incorrect. The new file is not recommended
for ordinary use and its entries are not installed by default.
(Thanks to Lester Caine for the high-quality Jersey, Guernsey, and
Isle of Man entries.)"
Like Macau, a lot of historic data has been added and for databases
handling historic material it would be nice if there was a way to have
matching correct offsets? Or we ignore the builtd in tools and cintinue
to rely on external functions ...
To be honest, I think the majority of our users will have no need for
correct pre-1970 time zone data. I suspect none of the major database
provide it either.
Lets not get hung up on these esoteric parts of time zones.
Mark
--
Mark Rotteveel
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