Re: Wrong times for sunrise/sunset?

[Marcin Borkowski]

On 2019-01-19, at 20:17, Pierpaolo Bernardi <olopierpa@gmail.com> wrote:

> Il giorno 19 gennaio 2019, alle ore 16:27, Marcin Borkowski <mbork@mbork.pl> 
> ha scritto:
>
>>Hello,
>>C-u M-x sunrise-sunset (and today's date) says
>
>>I also noticed that other online services give yet other results.
>>Anybody knows why the difference(s)?
>
> See https://lists.gnu.org/archive/html/help-gnu-emacs/2016-07/msg00321.html
>
> Hth

Yes, that helps, thanks.

Out of curiosity - Michael Heerdegen writes there:

--8<---------------cut here---------------start------------->8---
AFAIK the Emacs calculation is exact - it respects all astronomical
effects I know of.  But it doesn't try hard to round to whole minutes
correctly, so the result may differ from the actual event by an epsilon,
where epsilon < 1 min I think.
--8<---------------cut here---------------end--------------->8---

But the differences I can see are a few minutes.  Why, after takign care
of all astronomical effects, is "rounding to whole minutes correctly"
even an issue?

(I understand that I know very little abot time calculations and such,
and I understand they are difficult.  I'd just like to know.)

Best,

--
Marcin Borkowski
http://mbork.pl