calendar.json

{
  "09": {
    "01": "Some text for 09-01",
    "02": "Some text for 09-02",
    "03": "Some text for 09-03",
    "11": "Some text for 09-11"
  },
  "10": {
    "01": "Some text for 10-01", 
    "02": "Some text for 10-02"
  }
}

core.clj

(ns some.core
  (:use [clj-time.local])
  (:use [clojure.data.json])
  (:use [clojure.java.io])
  (:use [clojure.string :only [split]]))

(def parse-date
  (let [date (drop 1 (split (format-local-time (local-now) :date) #"-"))
        month (first date)
        day (last date)]
        [month day]))

(def load-json
  (read-json (reader "resources/calendar.json")))

(def get-data-from-json
  (let [day (keyword (first parse-date))
        month (keyword (last parse-date))]
        (-> load-json month day)))

;; Assuming that today is 2012-09-12
;; get-data-from-json => Some text for 10-01