[tz] Irish Standard Time vs Irish Summer Time

[Robert Elz]

  Date: Sat, 20 Jan 2018 01:39:50 +0000 (UTC)
  From: Joseph Myers <jsm at polyomino.org.uk>
  Subject: Re: [tz] Irish Standard Time vs Irish Summer Time

  | That's essentially why I think tm_isdst should be based on something
  | other than the notion of one time offset being standard and another
  | being a variant on that.

I don't disagree with anything that you say, but I'd go one step
further, and simply deprecate tm_isdst - it no longer serves any
necessary useful purpose at all (and anyone who believes it does
is not understanding its purpose).   [Those who still need it for
its original purpose should adopt tm_zone and tm_gmtoff instead.]

We can't just delete it, as it is in C and POSIX stds, but we can
tell people not to use it.

kre