As of time 0.3.36, any method that requires the system's local offset will fail on multithreaded unix-like systems, but this is not mentioned in the documentation for the local-offset feature, or any of the relevant methods.

Places where this should hopefully be documented:

The description of the local-offset feature
The documentation for time::UtcOffset::local_offset_at and time::UtcOffset::current_local_offset
The documentation for time::OffsetDateTime::now_local

288c942a34e19fa38704bdde5e1d49fc21318be2.

However, this documentation was removed in https://github.com/time-rs/time/commit/b513927af2e2a48b87a5374510abf9e703422d36, and replaced with "Without [unsound_local_offset], any method that requires the local offset will return the Err variant." in the crate-level documentation.

Later, https://github.com/time-rs/time/commit/110e17bb8461816551f7197a2aa2e34c981fa22d fully removed the reference to the local offset methods failing by default.

At this point, there is no documentation of the default behavior in places where people would look -- in the documentation of the local-offset feature or in the documentation of the methods that will fail, leading to a large number of issues asking about it: #591 #457 #297 #617 #538 #427 #645

I'm open to making a PR to add documentation, but it'll likely need to be carefully phrased.

time-rs / time

Document status of local-offset support #687

297 gives a good description of this problem; it was closed after adding documentation in https://github.com/time-rs/time/commit/288c942a34e19fa38704bdde5e1d49fc21318be2.