On Mon, 3 Mar 2025 at 21:24, Matt Johnson-Pint via tz <tz@iana.org> wrote:
Yes. Australia/Lord_Howe currently has a 30-minute difference between its standard and daylight times. Also, Antarctica/Troll has a 2-hour difference.
I'm not sure if there's an easy way to determine this directly from the tz files, but since the data is also parsed and distributed through various platforms, languages, libraries, and tools, it's probably something you could do externally. For example, you could probably write some Python script with zoneinfo data, which originates from here.
Those are the only two examples according to this C++ program: #include <chrono> #include <print> int main() { using namespace std::chrono; sys_days summer(2025y/6/21), winter(2025y/12/21); const auto& db = get_tzdb(); std::println("{}", db.version); for (const auto& tz : db.zones) { auto info1 = tz.get_info(summer); auto info2 = tz.get_info(winter); if (info1.offset != info2.offset) { if (abs(info1.offset - info2.offset) != 1h) std::println("{} has offset {} in summer and {} in winter", tz.name(), info1.offset, info2.offset); } } } The output on my system was: 2025a Antarctica/Troll has offset 7200s in summer and 0s in winter Australia/Lord_Howe has offset 37800s in summer and 39600s in winter