Subject: [Tzdist] draft-ietf-tzdist-service 4.1.3. Conditional Time Zone Requests - even year-to-year?

From: Tobias Conradi <[email-masked]>
Date: Sun, 21 Sep 2014 05:28:10 +0200

Time zone data is generally slow moving, with the set of time zones
   that change from even year-to-year being relatively small.

even year-to-year?

-- 
Tobias Conradi
Rheinsberger Str. 18
10115 Berlin
Germany

http://tobiasconradi.com

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From: Cyrus Daboo <[email-masked]>
Date: Sun, 21 Sep 2014 10:52:24 -0400

Hi Tobias,

>    that change from even year-to-year being relatively small.

I propose changing that to:

Time zone data is generally slow moving, with the set of time zones that 
change during the course of a year being relatively small.

-- 
Cyrus Daboo

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From: Tobias Conradi <[email-masked]>
Date: Sun, 21 Sep 2014 17:43:04 +0200

> change during the course of a year being relatively small.

Maybe

Time zone data is generally slow moving, in the years from 2004 to
2013 the maximum number of changed time zones during one year was:
<maximum number of changed time zones during one year>

Can someone obtain such a value? That would help to verify it is
indeed "slow moving" and give any reader the ability to better
understand the statement. Readers may have very different expectation
of what constitutes few changes and many changes.

-- 
Tobias Conradi
Rheinsberger Str. 18
10115 Berlin
Germany

http://tobiasconradi.com

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From: Lester Caine <[email-masked]>
Date: Sun, 21 Sep 2014 17:01:20 +0100

> of what constitutes few changes and many changes.

That depends on the data publisher rather than the tzdist protocol?

'The published changes to time zone data each year is relatively small
with many not having changed since originally defined. Some time zones
are however subject to annual variation at short notice due to the
astronomical variations in their definition.'

We do have the entire history of the change logs for tz in various
formats but extracting exact numbers of variations for each tzid would
require a little work since changes to both comments and raw data are
mixed up.

-- 
Lester Caine - G8HFL
-----------------------------
Contact - http://lsces.co.uk/wiki/?page=contact
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Rainbow Digital Media - http://rainbowdigitalmedia.co.uk

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From: Tobias Conradi <[email-masked]>
Date: Sun, 21 Sep 2014 18:34:46 +0200

> That depends on the data publisher rather than the tzdist protocol?
Oh, I missed that.

Fixing my statement:

Time zone data in some databases is generally slow moving, in the
years from 2004 to
2013 the maximum number of changed time zones in the IANA time zone
database during one year was:
<maximum number of changed time zones during one year in the IANA time
zone database>

> require a little work since changes to both comments and raw data are
Are the comments related to one time zone part of "time zone data" for
that time zone?

If yes, one would not need to un-mix them.

Having a quantity for change time zones including changes to comments
would at least give an upper bound for the value one is looking for.

-- 
Tobias Conradi
Rheinsberger Str. 18
10115 Berlin
Germany

http://tobiasconradi.com

---

From: Lester Caine <[email-masked]>
Date: Sun, 21 Sep 2014 19:28:22 +0100

> would at least give an upper bound for the value one is looking for.

hg.lsces.org.uk/hg/tzdata/ is my own attempt to monitor the changes and
does need a bit of tidy-up, but essentially each update to the tz
database only affects a few data sets each time, and many of the recent
changes are only relevant to pre 1970 data, simply tidying up data in
the light of revised provenance, with only 9 releases last year, and 7
so far this year.

The 2014g update is not a typical update, having all of the missing
historic material added back, but selecting previous version from the
yellow tag buttons will give a cleaner example.

My own 'plan' is that we should have an 'update' timeline for each
timezone along with the timeline for the data itself with source
material documented against the updates ... but that is a publishing
view rather than tzdist :)