<<On Fri, 4 Nov 2022 09:36:25 +0000, "Austin Group Bug Tracker via austin-group-l at The Open Group" <austin-group-l@opengroup.org> said:
> As I understand it, this requires that if mktime() determines that DST is > in effect, it returns the same result as it would for tm_isdst=1, otherwise > it returns the same result as it would for tm_isdst=0. That is how all > certified UNIX and POSIX systems behave. Until now I thought it was how all > mktime() implementations behave, but I see that the C DR that you cite > mentions "Arthur David Olson's popular ``tz'' time zone software" as > returning -1. That was back in 1994, so I wonder if it still does or if it > has changed to behave like other implementations. As a practical matter, although now maintained by Paul Eggert and under the auspices of IANA, this Reference Implementation, known as "tzcode", is used by many if not most platforms, and has been for many many years. I believe as a normative matter that if the standard disagrees on this qusstion, the standard is wrong. -GAWollman
