P0355R7: Extending chrono to Calendars and Time Zones

[cjdb]

Link: https://wg21.link/p0355r7

The status page notes that:

P0355: The implementation status is:

• Calendars mostly done in Clang 7
• Input parsers not done
• Stream output Obsolete due to P1361R2 “Integration of chrono with text formatting”
• Time zone and leap seconds In Progress
• UTC clock Clang 20
• TAI clock Clang 21
• GPS clock [libc++][chrono] implements GPS clock. #125921

BEGIN-RST-NOTES
See the `Github issue <https://github.com/llvm/llvm-project/issues/99982>`__ for detailed status
END-RST-NOTES

[llvmbot]

@llvm/issue-subscribers-c-20

Author: Christopher Di Bella (cjdb)

The [status page](https://libcxx.llvm.org/Status/Cxx20.html#note-p0355) notes that:

> P0355: The implementation status is:
> * Calendars mostly done in Clang 7
> * Input parsers not done
> * Stream output Obsolete due to P1361R2 “Integration of chrono with text formatting”
> * Time zone and leap seconds In Progress
> * TAI clock not done
> * GPS clock not done
> * UTC clock not done

[mordante]

It is 2025 and Clang still cannot std::chrono::parse() (C++20 feature)

This issue is meant to track the status of the implementation. Please don't post unrelated comments.

[bebuch]

Isn't clock_cast/clock_time_conversion missing here? It's an essential part of the paper which is still missing in libc++.