bug#34315: [PATCH] icalendar.el: DURATION fix + more robust timezone handling

[Eli Zaretskii]

> Date: Mon, 18 Feb 2019 20:15:19 +0100
> From: thunk2@arcor.de (Thomas Plass)
> Cc: 34315@debbugs.gnu.org
> 
> Eli Zaretskii wrote at 17:59 on February 18, 2019:
> : these capabilities are not propagated to C runtime
> : functions which Emacs uses.
> 
> I take it then, Windows pre-built users have no way to work around
> this in Elisp?

Not in Lisp, no.

> What about the C source?  Is there any way for a total C-dummy like me
> to tweak/hard wire a rule for my local zone into the source?  Could
> you point me at the file(s)/place(s) in the Git that I'd need to look
> at?

I don't understand what kind of C-level change do you have in mind.
AFAIU, any change to support this stuff would involve writing (or
importing from a free source) a parser for such DST rules, and then
using APIs like SetDynamicTimeZoneInformation to make the parsed rule
in effect.  It would probably also mean replacing localtime and its
ilk with versions that actually access the DST data set by the above
APIs.  Is that what you had in mind?