Re: [PATCH] manual: Add more documentation for the tm_isdst member of struct tm

[Florian Weimer <fweimer@redhat.com>]

* Paul Eggert:

>> Maybe we should just document that applications should set this field to
>> -1 when constructing struct tm data?
>
> Yes, if you're deriving struct tm data from the outside world and you
> have no idea what tm_isdst etc. should be, your apps should set
> tm_isdst to -1. However, if the outside world tells you tm_gmtoff
> (which is pretty common these days, e.g., see the "Date:" line in this
> email), then your apps should also set tm_gmtoff to what the outside
> world tells you, before you call mktime.

Okay, that would indeed be helpful advice.  I'll see if I can come up
with a new patch.

>> In case of Ireland it seems an artificial complication, though.  The
>> perception seems to be that IST is summer time, not standard time
>
> My impression is different, in that people in Ireland typically say
> "summer time" or "winter time". They typically do not say "standard 
> time" or "daylight saving time". And as it happens, summer time =
> standard time in Ireland.

I think RTE is not exactly fringe media in Ireland, and they recently
wrote (largely copying from last year I admittedly):

| When do the clocks change in Ireland in 2022?
|
| Daylight saving time in Ireland began (went forward an hour) at 01:00
| on Sunday, 27 March 2022 and will end (go back an hour) at 02:00 on
| Sunday, 30 October 2022.

<https://www.rte.ie/lifestyle/living/2022/0309/1285354-everything-you-need-to-know-about-the-clocks-changing-in-2022/>

This is not just one journalist making an error.  I think the cultural
convention *is* different.

Thanks,
Florian