Environment: Windows 10 x64 MSVC Version 17.12.4 It;'s possible to pass a `std::chrono::local_seconds` object to `format` that has an ambiguous time, so for example ~2am on April 6th 2025 in Sydney daylight savings ends. Sample Code (note, system running must be on AEDT) ``` #include <chrono> #include <cstdlib> #include <iostream> #include <fmt/core.h> #include <fmt/chrono.h> int main() { const auto& timeZoneDatabase = std::chrono::get_tzdb(); const auto& currentZone = timeZoneDatabase.current_zone(); std::cout << currentZone->name() << '\n'; // This needs to be Australia/Sydney uint64_t two_in_the_morning = 1743865205; // just after 2am on 2025/4/6 which is a daylight savings changeover point auto dur = std::chrono::duration<uint64_t>(two_in_the_morning); auto time_point = std::chrono::time_point<std::chrono::system_clock, std::chrono::duration<uint64_t>>(dur); auto time_point_as_local_seconds = currentZone->to_local(std::chrono::floor<std::chrono::seconds>(time_point)); std::string text = fmt::format("{:%Y-%m-%d %H:%M:%S}", time_point_as_local_seconds); std::cout << text << '\n'; return 0; } ``` This block here seems to be the cause: https://github.com/fmtlib/fmt/blob/94ab51cb8c63c93220f0cdd1733bdeef95e77d60/include/fmt/chrono.h#L575-L580 `to_sys` can throw exceptions in these cases, and needs to be passed `std::chrono::choose`
