From: Paul Eggert <eggert@cs.ucla.edu> Date: Sat, 27 Jan 2018 18:22:08 -0800 Subject: Re: [tz] OpenJDK/CLDR/ICU/Joda issues with Ireland change | However, they do not suffice for tzdata, since they assume at | most two types of time can exist in a timezone_t object, Actually, they don't, if zic set the isdst field in the ttinfo to 0, 1, 2, 3, ... (allowed by POSIX< which just requires "positive" "negative" and "zero") then the functions would fetch the corresponding value (they don't really access tzname[] and timezone!) | So code should not use these functions if it wants to work on | arbitrary timestamps. But I agree with that, as there's no reason we cannot have isdst value 1 with various different gmt offsets at different periods (like when a zone has altered its base offset), and there's no way with those functions to specify which one is wanted, nor to doscover which was used for the result. | Also, even if one assumes POSIX, tzgetgmtoff and tzgetname | are not much use on platforms like NetBSD that have | tm_gmtoff and tm_zone. They're less than "not much use", they are useless. kre