Rust time crate Rfc3339 accepts any byte as the date/time separator

time 0.3.55's OffsetDateTime::parse(s, &Rfc3339) skips the byte between date and time without checking it (deliberate since time-rs/time#700, to support space separators for rusqlite), so '2062-01-31-10:07:59Z', '2062-01-31x10:07:59Z' and '2062-01-31_10:07:59Z' all parse as valid. If you use it as a validator (API input, JSON Schema date-time), check s.as_bytes()[10] is one of b'T', b't', b' ' yourself. In the same differential run (5000 generated strings plus edge cases against an exact RFC 3339 oracle), chrono parse_from_rfc3339 accepts :60 at any time of day (its documented leap-second representation, nanos=1e9), humantime rejects every offset except Z, and none of chrono/time/jiff/speedate returned a wrong instant.