zoned_time

[LukashonakV]

Hi @vitaut , this PR provides zoned_time formatter.

---

#include <fmt/chrono.h>  
#include <spdlog/spdlog.h>  

using namespace std::chrono;  

int main(int argc, char* argv[]) {
  const std::chrono::zoned_time now{locate_zone("America/Chicago"),
                       floor<seconds>(system_clock::now())};
  std::string fmt_result{fmt::format("{:%H:%M %Z %z}", now)};
  std::string std_result{std::format("{:%H:%M %Z %z}", now)};

  spdlog::info("\nfmt_result: {}\nstd_result: {}", fmt_result, std_result);
  return 0;
}

With the result:

[2026-01-09 02:09:56.643] [info] 
fmt_result: 17:09 CST -0600
std_result: 17:09 CST -0600

[vitaut]

The formatter should be conditionally defined since zoned_time is a C++20 feature.

[LukashonakV]

Hi @vitaut , yes I've checked CI logs and is trying to solve it

[LukashonakV]

Now it should be fine.

[LukashonakV]

Hi @vitaut , can you please review once again, when you have a time of course. Thanks)