[tz] Timezone in Brazil

Lester Caine lester at lsces.co.uk
Sun Oct 11 20:11:22 UTC 2015

On 11/10/15 17:19, Guy Harris wrote:
>> That these rules ONLY apply to time data later than 1970 sweeps the
>> > problem of identifying just were some places were located earlier than
>> > that under the carpet,
> I think that's the intent - to keep it out of scope of the tzdb.  As Paul has noted, the further we go back in time, the harder it is to find *correct* time zone information.  Go back far enough, and there *is* no standard time, and the "tzid" would end up being a longitude+latitude and you'd just calculate local time from that.

I've no argument with that ... It does not however replace the need for
a reliable source of data on when locations started using a standardised
time, which has been evolving as more historic material is scanned and
translated, and more important where proven reliable pre-1970's data
exists but is not provided via tzdb ... If one is working with historic
material but other users have a less than complete set of tz data we
have confusion when things disagree, so some flag that data is 'unknown'
is essential in those circumstances.

With tzdist I would contest that tzdb should only be published with a
1970 start date and anything prior to that is unreliable.

Lester Caine - G8HFL
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