What it does Duckling parses fuzzy human text—dates, durations, temperatures—into structured maps with typed values and “grain” precision. Feed it “the first Tuesday of October” and get back an ISO timestamp plus :day granularity. It shipped with multilingual support out of the box.

The interesting bit The whole API surface is two functions: load! and parse. That’s either elegant minimalism or a sign that the real complexity lives in the undocumented rule engine. The README hints at :time, :duration, :temperature and more, but never lists them exhaustively.

Key highlights

• Supports English, French, Spanish, Chinese, and likely others via :xx$core configurations
• Returns byte offsets (:start / :end) for the matched substring, useful for highlighting
• Grain system (:day, :hour) lets downstream code know how precise to get
• Published to Clojars; one dependency away in a project.clj
• Live playground existed at duckling.wit.ai (status unknown)

Caveats

• Deprecated since May 2017; Facebook explicitly moved to a new Haskell implementation
• README is essentially a quickstart card; no architecture docs, no rule-writing guide
• The load! side effect and global state won’t win functional purists

Verdict Worth studying if you’re building a date-time parser and want to see how much complexity two functions can paper over. Skip it for production unless you’re already committed to maintaining a dead fork.