"Could not determine the UTC offset on this system" and defaulting to UTC timestamps

[borntyping]

The current defaults are to format timestamps using the local timezone. Since switching to the time crate to avoid unsafe code in chrono (CVE-2020-26235), a lot of users use simple_logger in scenarios where time refuses to fetch the local timezone to avoid running unsafe code (time-rs/time#293). This usually affects users running a multithreaded application, as time assumes it's safe to get the local timezone when running in a single-threaded environment where there's no risk of an environment variable being set by a different thread.

Support for UTC timestamps has been added to simple_logger, but I'm currently trying to work out the best way to safely change the default away from local timestamps in a way that doesn't risk silently changing user's logs from one timezone to another with no way to tell the difference.

If this issue is affecting you, there are a few approaches you can take:

1. Upgrade to simple_logger 2.0.0
   This breaking change switches to UTC timestamps in RFC 3339 format.
2. Switch the timestamp display
   Use UTC via .with_utc_timestamps() like in examples/timestamps_utc.rs.
   Use a static UTC offset via .with_utc_offset(...) like in examples/timestamps_utc_offset.rs.
   Don't display timestamps at all via .without_timestamps() like in examples/timestamps_none.rs.
3. Use the time crate's unsafe features
   Export RUSTFLAGS="--cfg unsound_local_offset" when compiling (docs).

Issues related to this are all tagged CVE-2020-26235. Tagging #51, #48, #47, #44, #43, #35.