humantime

humantime parses and formats Rust’s standard-library Duration and SystemTime types using human-friendly notation, such as 15days 2min 2s for durations and RFC 3339 timestamps like 2018-01-01T12:53:00Z. It’s designed to be extremely fast since the timestamp format it produces and consumes is effectively fixed, avoiding the overhead of general-purpose calendar libraries for the common case of reading/writing timestamps and durations in config files, logs, and CLIs.

Maintained under the chronotope organization (which also maintains the chrono date/time crate), humantime is a small, stable, widely depended-upon utility crate with nearly 400 million total downloads, commonly pulled in as a dependency of logging and CLI-configuration crates like env_logger.

What You Get

• parse_duration() / format_duration() - free-form duration notation like 15days 2min 2s in both directions
• parse_rfc3339() / format_rfc3339() - RFC 3339 timestamp parsing and formatting for SystemTime, benchmarked far faster than general calendar libraries for this fixed format
• A weaker timestamp parser accepting space-separated dates like 2018-01-01 12:53:00
• Duration/Timestamp wrapper types implementing FromStr/Display for direct use with clap argument parsing or serde
• Companion crate humantime-serde for direct serde integration (the README notes the older serde-humantime crate is unmaintained)

Common Use Cases

• Parsing CLI flags like --timeout 30s or --retention 7days into std::time::Duration via clap integration
• Reading/writing human-readable durations and timestamps in config files (YAML/TOML) without pulling in a full calendar library
• Formatting log timestamps in RFC 3339 with minimal overhead — used internally by env_logger for its timestamp output
• Any place a Rust program needs quick, allocation-light SystemTime/Duration <-> string conversion

Under The Hood

Architecture - The crate is small and focused: duration.rs implements the free-form duration grammar (parsing tokens like 15days, 2min) and its formatter, date.rs implements the RFC 3339 timestamp parser/formatter plus the looser space-separated variant, and wrapper.rs provides the newtype wrappers (Duration, Timestamp) implementing FromStr/Display so the crate’s types slot directly into clap or serde without adapter code. Tech Stack - Zero required runtime dependencies beyond std; dev-dependencies include bencher for micro-benchmarks and the time crate (for comparison benchmarks against chrono/time in benches/), edition 2021, MSRV 1.60, dual MIT/Apache-2.0 licensed. Code Quality - date.rs and duration.rs carry 26 and 14 inline #[test] functions respectively covering parse/format round-trips and edge cases; the README documents concrete benchmark numbers (e.g. RFC 3339 parsing at ~24-36ns/iter versus ~737ns/iter for chrono) demonstrating the performance claims are backed by tracked benchmarks rather than assertions. API Design - The API is deliberately minimal — four core functions plus two wrapper types — favoring a handful of well-named free functions over a builder or configuration object, which keeps the learning curve low at the cost of configurability (e.g. the timestamp format is effectively fixed rather than customizable).