This documents deals with how to manipulate Date and Time in clojure.

To use this in your application go to your project.clj file and include [clj-time "<version_number>"] in your :dependencies section.

Creating a Joda Time

(clj-time/date-time 2017 1 20)

Gives you a Joda time of 20th Jan 2017 at 00:00:00.

Hours, minutes and seconds can also be specified as

(clj-time/date-time year month date hour minute second millisecond)

Getting Day Month Year Hour Minute Second from your date-time

(require '[clj-time.core :as t])

(def example-time (t/date-time 2016 12 5 4 3 27 456))

(t/year example-time) ;; 2016
(t/month example-time) ;; 12
(t/day example-time) ;; 5
(t/hour example-time) ;; 4
(t/minute example-time) ;; 3
(t/second example-time) ;; 27

Comparing two date-time

(require '[clj-time.core :as t])

(def date1 (t/date-time 2016 12 5))
(def date2 (t/date-time 2016 12 6))

(t/equal? date1 date2) ;; false
(t/equal? date1 date1) ;; true

(t/before? date1 date2) ;; true
(t/before? date2 date1) ;; false

(t/after? date1 date2) ;; false
(t/after? date2 date1) ;; true

Checking whether a time is within a time interval

This function tells whether a given time lies within a a given time interval.

(require '[clj-time.core :as t])

(def date1 (t/date-time 2016 11 5))
(def date2 (t/date-time 2016 12 5))

(def test-date1 (t/date-time 2016 12 20))
(def test-date2 (t/date-time 2016 11 15))

(t/within? (t/interval date1 date2) test-date1) ;; false
(t/within? (t/interval date1 date2) test-date2) ;; true

The interval function is used is exclusive, which means that is does not include the second argument of the function within the interval. As an example:

(t/within? (t/interval date1 date2) date2) ;; false
(t/within? (t/interval date1 date2) date1) ;; true

Adding joda date-time from other time types

The clj-time.coerce library can help converting other date-time formats to joda time format (clj-time.core/date-time). The other formats include Java long format, String, Date, SQL Date.

To convert time from other time formats, include the library and use the from- function, e.g.

(require '[clj-time.coerce :as c])

(def string-time "1990-01-29")
(def epoch-time 633571200)
(def long-time 633551400)

(c/from-string string-time) ;; #<DateTime 1990-01-29T00:00:00.000Z>
(c/from-epoch epoch-time) ;; #<DateTime 1990-01-29T00:00:00.000Z>
(c/from-long 633551400) ;; #<DateTime 1990-01-29T00:00:00.000Z>

Adding date-time to other date-times

cljs-time gives us option to add/subtract date-times to other date-times. The date times added subtracted should be in form of days, months, years, hours etc.

(require '[clj-time.core :as t])

(def example-date (t/date-time 2016 1 1)) ;; #<DateTime 2016-01-01T00:00:00.000Z>

;; Addition
(t/plus example-date (t/months 1))        ;; #<DateTime 2016-02-01T00:00:00.000Z>
(t/plus example-date (t/years 1))         ;; #<DateTime 2017-01-01T00:00:00.000Z>

;; Subtraction
(t/minus example-date (t/days 1))          ;; #<DateTime 2015-12-31T00:00:00.000Z>
(t/minus example-date (t/hours 12))        ;; #<DateTime 2015-12-31T12:00:00.000Z>