diff --git a/README.md b/README.md
index c9b4f29..c20557a 100644
--- a/README.md
+++ b/README.md
@@ -30,21 +30,21 @@ A Clojure library for JSON Web Token(JWT) [draft-ietf-oauth-json-web-token-19](h
 (def claim
   {:iss "foo"
    :exp (plus (now) (days 1))
-   :nbf (now)})
+   :iat (now)})
 
 (def rsa-prv-key (private-key "rsa/private.key" "pass phrase"))
 (def ec-prv-key  (private-key "ec/private.key"))
 
-; plain JWT
+;; plain JWT
 (-> claim jwt to-str)
 
-; HMAC256 signed JWT
+;; HMAC256 signed JWT
 (-> claim jwt (sign :HS256 "secret") to-str)
 
-; RSA256 signed JWT
+;; RSA256 signed JWT
 (-> claim jwt (sign :RS256 rsa-prv-key) to-str)
 
-; ECDSA256 signed JWT
+;; ECDSA256 signed JWT
 (-> claim jwt (sign :ES256 ec-prv-key) to-str)
 ```
 
@@ -60,22 +60,26 @@ A Clojure library for JSON Web Token(JWT) [draft-ietf-oauth-json-web-token-19](h
 (def claim
   {:iss "foo"
    :exp (plus (now) (days 1))
-   :nbf (now)})
+   :iat (now)})
 
 (def rsa-prv-key (private-key "rsa/private.key" "pass phrase"))
 (def rsa-pub-key (public-key  "rsa/public.key"))
 (def ec-prv-key  (private-key "ec/private.key"))
 (def ec-pub-key  (public-key  "ec/public.key"))
 
+;; verify plain JWT
 (let [token (-> claim jwt to-str)]
   (-> token str->jwt verify))
 
+;; verify HMAC256 signed JWT
 (let [token (-> claim jwt (sign :HS256 "secret") to-str)]
   (-> token str->jwt (verify "secret")))
 
+;; verify RSA256 signed JWT
 (let [token (-> claim jwt (sign :RS256 rsa-prv-key) to-str)]
   (-> token str->jwt (verify rsa-pub-key)))
 
+;; verify ECDSA256 signed JWT
 (let [token (-> claim jwt (sign :ES256 ec-prv-key) to-str)]
   (-> token str->jwt (verify ec-pub-key)))
 ```
diff --git a/project.clj b/project.clj
index 7bf2915..910cae2 100644
--- a/project.clj
+++ b/project.clj
@@ -1,4 +1,4 @@
-(defproject clj-jwt "0.0.5"
+(defproject clj-jwt "0.0.6"
   :description  "Clojure library for JSON Web Token(JWT)"
   :url          "https://github.com/liquidz/clj-jwt"
   :license      {:name "Eclipse Public License"
diff --git a/src/clj_jwt/core.clj b/src/clj_jwt/core.clj
index 68ec02b..11233f9 100644
--- a/src/clj_jwt/core.clj
+++ b/src/clj_jwt/core.clj
@@ -2,7 +2,7 @@
   (:require
     [clj-jwt.base64    :refer [url-safe-encode-str url-safe-decode-str]]
     [clj-jwt.sign      :refer [get-signature-fn get-verify-fn supported-algorithm?]]
-    [clj-time.coerce   :refer [to-long]]
+    [clj-jwt.intdate   :refer [joda-time->intdate]]
     [clojure.data.json :as json]
     [clojure.string    :as str]))
 
@@ -10,8 +10,6 @@
 (def ^:private map->encoded-json (comp url-safe-encode-str json/write-str))
 (def ^:private encoded-json->map (comp #(json/read-str % :key-fn keyword) url-safe-decode-str))
 (defn- update-map [m k f] (if (contains? m k) (update-in m [k] f) m))
-(defn- joda-time? [x] (= org.joda.time.DateTime (type x)))
-(defn- to-intdate [d] {:pre [(joda-time? d)]} (int (/ (to-long d) 1000)))
 
 (defrecord JWT [header claims signature])
 
@@ -28,7 +26,7 @@
 (extend-protocol JsonWebToken
   JWT
   (init [this claims]
-    (let [claims (reduce #(update-map % %2 to-intdate) claims [:exp :nbf :iat])]
+    (let [claims (reduce #(update-map % %2 joda-time->intdate) claims [:exp :nbf :iat])]
       (assoc this :header {:alg "none" :typ "JWT"} :claims claims :signature "")))
 
   (encoded-header [this]
diff --git a/src/clj_jwt/intdate.clj b/src/clj_jwt/intdate.clj
new file mode 100644
index 0000000..ac2b32f
--- /dev/null
+++ b/src/clj_jwt/intdate.clj
@@ -0,0 +1,16 @@
+(ns clj-jwt.intdate
+  (:require
+    [clj-time.coerce :refer [to-long from-long]]))
+
+(defn- joda-time? [x] (= org.joda.time.DateTime (type x)))
+
+(defn joda-time->intdate
+  [d]
+  {:pre [(joda-time? d)]}
+  (int (/ (to-long d) 1000)))
+
+
+(defn intdate->joda-time
+  [i]
+  {:pre [(integer? i) (pos? i)]}
+  (from-long (* i 1000)))
diff --git a/test/clj_jwt/intdate_test.clj b/test/clj_jwt/intdate_test.clj
new file mode 100644
index 0000000..06b9127
--- /dev/null
+++ b/test/clj_jwt/intdate_test.clj
@@ -0,0 +1,17 @@
+(ns clj-jwt.intdate-test
+  (:require
+    [clj-jwt.intdate :refer :all]
+    [clj-time.core   :refer [date-time]]
+    [midje.sweet     :refer :all]))
+
+(fact "joda-time->intdate should work fine."
+  (let [d (date-time 2000 1 2 3 4 5)]
+    (joda-time->intdate d)   => 946782245
+    (joda-time->intdate nil) => (throws AssertionError)))
+
+(fact "intdate->joda-time should work fine."
+  (let [d (date-time 2000 1 2 3 4 5)
+        i (joda-time->intdate d)]
+    (intdate->joda-time i)   => d
+    (intdate->joda-time nil) => (throws AssertionError)))
+