Clojure:
Parsing a date from a string

How to:

Clojure, being a JVM language, allows you to use Java’s date and time libraries directly. Let’s start with the built-in Java interoperation and then explore how to utilize a popular third-party library, clj-time, for more idiomatic Clojure solutions.

Using Java Interop

Clojure can directly leverage Java’s java.time.LocalDate for parsing dates from strings:

(require '[clojure.java.io :as io])

; Parsing a date using Java interop
(let [date-str "2023-04-01"
      date (java.time.LocalDate/parse date-str)]
  (println date))
; Output: 2023-04-01

Using clj-time

A more idiomatic Clojure library for dealing with dates and times is clj-time. It wraps Joda-Time, a comprehensive library for date and time operations. First, you’ll need to add clj-time to your project’s dependencies. Here’s how you parse a date string using clj-time:

; Make sure to add [clj-time "0.15.2"] to your project.clj under :dependencies

(require '[clj-time.format :as fmt]
         '[clj-time.core :as time])

; Define a formatter
(let [formatter (fmt/formatter "yyyy-MM-dd")
      date-str "2023-04-01"
      parsed-date (fmt/parse formatter date-str)]
  (println parsed-date))
; Output: #object[org.joda.time.DateTime 0x76eccb5d "2023-04-01T00:00:00.000Z"]

These examples demonstrate basic date parsing. Both methods are useful, but clj-time can provide a more Clojure-centric approach with additional functionalities for complex requirements.