[tz] [PROPOSED] New edition of Calendrical Calculations

Brian Inglis Brian.Inglis at SystematicSw.ab.ca
Tue Apr 3 18:50:17 UTC 2018

On 2018-04-03 10:34, John Layt wrote:
> On 3 April 2018 at 06:25, Paul Eggert wrote:
>> * theory.html (Calendrical issues):
>> Update Reingold & Dershowitz citation to 4th edition.
>> ---
>>  theory.html | 8 ++++----
>>  1 file changed, 4 insertions(+), 4 deletions(-)
>> diff --git a/theory.html b/theory.html
>> index 4d8726d..596b32c 100644
>> --- a/theory.html
>> +++ b/theory.html
>> @@ -1155,10 +1155,10 @@ based on guesswork and these guesses may be corrected or improved.
>>  Calendrical issues are a bit out of scope for a time zone database,
>>  but they indicate the sort of problems that we would run into if we
>>  extended the time zone database further into the past.
>> -An excellent resource in this area is Nachum Dershowitz and Edward M.
>> -Reingold, <cite><a
>> -href="https://www.cs.tau.ac.il/~nachum/calendar-book/third-edition/">Calendrical
>> -Calculations: Third Edition</a></cite>, Cambridge University Press (2008).
>> +An excellent resource in this area is Edward M. Reingold
>> +and Nachum Dershowitz, <cite><a
>> +href="https://www.cambridge.org/fr/academic/subjects/computer-science/computing-general-interest/calendrical-calculations-ultimate-edition-4th-edition">Calendrical
>> +Calculations: The Ultimate Edition</a></cite>, Cambridge University Press (2018).
>>  Other information and sources are given in the file '<code>calendars</code>'
>>  in the <code><abbr>tz</abbr></code> distribution.
>>  They sometimes disagree.

> Nice to see a new edition, but sadly the same use restrictions still apply,
> to quote:> "The Functions (code, formulas, and calendar data) contained in this book
> and/or provided on the publisher’s web site for this book were written by 
> Nachum Dershowitz and Edward M. Reingold (the “Authors”), who retain all 
> rights to them except as granted in the License and subject to the warranty 
> and liability limitations below. These Functions are subject to this book’s 
> copyright.> In case there is cause for doubt about whether a use you contemplate is
> authorized, please contact the Authors.> 1. LICENSE. The Authors grant you a license for personal use. This means that
> for strictly personal use you may copy and use the code and keep a backup or
> archival copy also. The Authors grant you a license for re-use within 
> non-commercial, non-profit software provided prominent credit is given and
> the Authors’ rights are preserved. Any other uses, including, without
> limitation, allowing the code or its output to be accessed, used, or
> available to others, are not permitted."> Basically means I've never been able to read it for fear of taint...
Erlang port published with same licence terms:


I doubt any issues with ports, as long as you don't publish the original Lisp,
which is pretty straightforward code (except for the need to express formulae as
Lisp expressions), or the output from the Lisp.
Many of the formulae are obvious, published in their own earlier or others'
works, or other public calendar software e.g. tzcode.
Uses of non-creative non-original common public factual data and mathematical
formulae (essential to all uses of calendars), including information from
reverse engineering, appear to be unrestricted, from what I gather (IANAL).

Why do you have a concern regarding taint?

Take care. Thanks, Brian Inglis, Calgary, Alberta, Canada

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