whichtime

High-performance natural language date parsing in Rust.

whichtime ships three intentional public Rust packages:

• whichtime: the recommended high-level Rust API
• whichtime-sys: the lower-level parsing engine crate
• whichtime-cli: a small CLI for quick parsing and smoke tests

Swift, Kotlin, and Python bindings are available as preview/source-build integrations until further testing is complete.

Documentation

• Guide: https://transcodeworks.github.io/whichtime/
• Rust docs (whichtime): https://docs.rs/whichtime
• Rust docs (whichtime-sys): https://docs.rs/whichtime-sys

Quick Start

Add whichtime to your Rust project:

[dependencies]
whichtime = "0.1"

use whichtime::WhichTime;

fn main() -> whichtime::Result<()> {
    let parser = WhichTime::new();

    if let Some(date) = parser.parse_date("tomorrow at 3pm", None)? {
        println!("{}", date.to_rfc3339());
    }

    if let Some(date) = parser.fr().parse_date("demain matin", None)? {
        println!("{}", date.to_rfc3339());
    }

    // Using a reference date
    let reference = chrono::Utc::now();
    if let Some(date) = parser.parse_date("tomorrow at 3pm", Some(reference))? {
        println!("{}", date.to_rfc3339());
    }

    Ok(())
}

Use whichtime-sys when you want direct access to the lower-level engine, or when you need to build a custom parser pipeline.

Install the CLI with:

cargo install whichtime-cli

Supported Expressions

whichtime can parse casual dates, relative dates, weekdays, explicit dates, time expressions, and date ranges such as:

• tomorrow at 3pm
• in 2 hours
• next Friday
• December 25th, 2026
• Monday to Friday

Supported Locales

The Rust crates currently support these locales:

• en English
• de German
• es Spanish
• fr French
• it Italian
• ja Japanese
• nl Dutch
• pt Portuguese
• ru Russian
• sv Swedish
• uk Ukrainian
• zh Chinese

Package Lineup

• whichtime: recommended high-level Rust API for application code
• whichtime-sys: lower-level parsing engine for direct parser access and custom integration work
• whichtime-cli: command-line interface that prints the first parsed timestamp as RFC 3339 in UTC
• whichtime-ffi: internal crate used for UniFFI bindings and shared cross-language transport types

Preview Bindings

The repository also contains Swift, Kotlin, and Python bindings.

• Swift: build the XCFramework locally with ./common/build-ios.sh
• Kotlin: generate bindings locally with ./common/build-kotlin.sh
• Python: build and install locally with ./common/build-python.sh

Development

cargo test --workspace --all-features
cargo fmt --all -- --check
cargo clippy --workspace --all-features -- -D warnings

To validate publishable crates locally:

cargo package -p whichtime-sys
cargo package --list -p whichtime
cargo package --list -p whichtime-cli

License

MIT. See LICENSE.

Acknowledgments

• chrono-node — The JavaScript library that inspired this project
• UniFFI — Mozilla's FFI bindings generator
• Ferrostar — Inspiration for project structure and build system