* Fix copy-paste damage in `formatter.tai_time.pass.cpp`.
+ Comparing the `#if` to the `#else` case, it's clear that this
half-copied check should be removed.
* Mark `is_steady` as `[[maybe_unused]]`.
+ It's only used within `LIBCPP_STATIC_ASSERT`.
Implements parts of:
- P0355 Extending <chrono> to Calendars and Time Zones
- P1361 Integration of chrono with text formatting
- LWG3359 <chrono> leap second support should allow for negative leap
seconds