Rust's `time` crate does have separate types for these:

    https://docs.rs/time/latest/time/struct.OffsetDateTime.html
    https://docs.rs/time/latest/time/struct.PrimitiveDateTime.html

It's not as helpful as you'd think IME - timezoneless date times are suprisingly niche (at least as a useful tool to intentionally choose, rather than an accidental side effect of API choice.)