bug#45818: 28.0.50; Test solar-sunrise-sunset fails

[Mattias Engdegård]

12 jan. 2021 kl. 21.06 skrev Basil L. Contovounesios <contovob@tcd.ie>:

> So I'm guessing dst-adjust-time adjusts for DST in my locale (based on
> some cache), but not yours?  The following change lets the test succeed
> for me:

Thank you, and I agree that it's probably the pragmatic choice. Much as I would 
have liked to track down and explain the exact reason for the observed 
phenomenon, I gave up and pushed your suggested patch.

If I would hazard a guess, it's related to the fact that Ireland uses daylight 
saving in winter (with opposite adjustment) rather than in summer; this may 
trigger a daylight-saving adjustment for the dates in question (late December). 
The fact that IST is used for both Irish and Indian time may be significant or 
a mere coincidence; it certainly didn't help matters.

Date and time calculations can be both infuriatingly and delightfully messy, 
but in this case the code didn't really help either, with way too many implicit 
input parameters -- global variables, caches, system settings, time-zone files, 
and so on. Not something to make a test writer happy!

Thanks again for the report, and for persevering!