diff --git a/Cargo.toml b/Cargo.toml
index 7b574a3..e724acd 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -4,4 +4,5 @@ version = "0.1.0"
 authors = ["Curtis McEnroe <programble@gmail.com>"]
 
 [dependencies]
+chrono = "0.2.17"
 url = "0.5.0"
diff --git a/src/client.rs b/src/client.rs
new file mode 100644
index 0000000..dff696b
--- /dev/null
+++ b/src/client.rs
@@ -0,0 +1,86 @@
+use url::{Url, ParseResult};
+
+/// OAuth 2.0 client.
+pub struct Client {
+    auth_uri: String,
+    token_uri: String,
+
+    client_id: String,
+    client_secret: String,
+    redirect_uri: Option<String>,
+}
+
+impl Client {
+    /// Creates an OAuth 2.0 client.
+    pub fn new<S: Into<String>>(
+        auth_uri: S,
+        token_uri: S,
+        client_id: S,
+        client_secret: S,
+        redirect_uri: Option<S>
+    ) -> Self {
+        Client {
+            auth_uri: auth_uri.into(),
+            token_uri: token_uri.into(),
+
+            client_id: client_id.into(),
+            client_secret: client_secret.into(),
+            redirect_uri: redirect_uri.map(Into::<String>::into),
+        }
+    }
+
+    /// Creates a Google OAuth 2.0 client.
+    pub fn google<S: Into<String>>(
+        client_id: S,
+        client_secret: S,
+        redirect_uri: Option<S>
+    ) -> Self {
+        Client {
+            auth_uri: String::from("https://accounts.google.com/o/oauth2/auth"),
+            token_uri: String::from("https://accounts.google.com/o/oauth2/token"),
+
+            client_id: client_id.into(),
+            client_secret: client_secret.into(),
+            redirect_uri: redirect_uri.map(Into::<String>::into),
+        }
+    }
+
+    /// Creates a GitHub OAuth 2.0 client.
+    pub fn github<S: Into<String>>(
+        client_id: S,
+        client_secret: S,
+        redirect_uri: Option<S>
+    ) -> Self {
+        Client {
+            auth_uri: String::from("https://github.com/login/oauth/authorize"),
+            token_uri: String::from("https://github.com/login/oauth/access_token"),
+
+            client_id: client_id.into(),
+            client_secret: client_secret.into(),
+            redirect_uri: redirect_uri.map(Into::<String>::into),
+        }
+    }
+
+    /// Constructs an authorization request URI.
+    pub fn auth_uri(&self, scope: Option<&str>, state: Option<&str>) -> ParseResult<String> {
+        let mut uri = try!(Url::parse(&self.auth_uri));
+
+        let mut query_pairs = vec![
+            ("response_type", "code"),
+            ("client_id", &self.client_id),
+        ];
+        if let Some(ref redirect_uri) = self.redirect_uri {
+            query_pairs.push(("redirect_uri", redirect_uri));
+        }
+        if let Some(scope) = scope {
+            query_pairs.push(("scope", scope));
+        }
+        if let Some(state) = state {
+            query_pairs.push(("state", state));
+        }
+
+        uri.set_query_from_pairs(query_pairs.iter());
+
+        Ok(uri.serialize())
+    }
+}
diff --git a/src/lib.rs b/src/lib.rs
index 57a8850..c9e8797 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,88 +1,9 @@
+extern crate chrono;
+extern crate hyper;
 extern crate url;
 
-use url::{Url, ParseResult};
+pub use client::Client;
+mod client;
 
-/// OAuth 2.0 client.
-pub struct Client {
-    auth_uri: String,
-    token_uri: String,
-
-    client_id: String,
-    client_secret: String,
-    redirect_uri: Option<String>,
-}
-
-impl Client {
-    /// Creates an OAuth 2.0 client.
-    pub fn new<S: Into<String>>(
-        auth_uri: S,
-        token_uri: S,
-        client_id: S,
-        client_secret: S,
-        redirect_uri: Option<S>
-    ) -> Self {
-        Client {
-            auth_uri: auth_uri.into(),
-            token_uri: token_uri.into(),
-
-            client_id: client_id.into(),
-            client_secret: client_secret.into(),
-            redirect_uri: redirect_uri.map(Into::<String>::into),
-        }
-    }
-
-    /// Creates a Google OAuth 2.0 client.
-    pub fn google<S: Into<String>>(
-        client_id: S,
-        client_secret: S,
-        redirect_uri: Option<S>
-    ) -> Self {
-        Client {
-            auth_uri: String::from("https://accounts.google.com/o/oauth2/auth"),
-            token_uri: String::from("https://accounts.google.com/o/oauth2/token"),
-
-            client_id: client_id.into(),
-            client_secret: client_secret.into(),
-            redirect_uri: redirect_uri.map(Into::<String>::into),
-        }
-    }
-
-    /// Creates a GitHub OAuth 2.0 client.
-    pub fn github<S: Into<String>>(
-        client_id: S,
-        client_secret: S,
-        redirect_uri: Option<S>
-    ) -> Self {
-        Client {
-            auth_uri: String::from("https://github.com/login/oauth/authorize"),
-            token_uri: String::from("https://github.com/login/oauth/access_token"),
-
-            client_id: client_id.into(),
-            client_secret: client_secret.into(),
-            redirect_uri: redirect_uri.map(Into::<String>::into),
-        }
-    }
-
-    /// Constructs an authorization request URI.
-    pub fn auth_uri(&self, scope: Option<&str>, state: Option<&str>) -> ParseResult<String> {
-        let mut uri = try!(Url::parse(&self.auth_uri));
-
-        let mut query_pairs = vec![
-            ("response_type", "code"),
-            ("client_id", &self.client_id),
-        ];
-        if let Some(ref redirect_uri) = self.redirect_uri {
-            query_pairs.push(("redirect_uri", redirect_uri));
-        }
-        if let Some(scope) = scope {
-            query_pairs.push(("scope", scope));
-        }
-        if let Some(state) = state {
-            query_pairs.push(("state", state));
-        }
-
-        uri.set_query_from_pairs(query_pairs.iter());
-
-        Ok(uri.serialize())
-    }
-}
+pub use token::Token;
+mod token;
diff --git a/src/token.rs b/src/token.rs
new file mode 100644
index 0000000..68c5be6
--- /dev/null
+++ b/src/token.rs
@@ -0,0 +1,17 @@
+use chrono::{DateTime, UTC};
+
+/// OAuth 2.0 access token.
+pub struct Token {
+    pub access_token: String,
+    pub token_type: String,
+    pub expires: Option<DateTime<UTC>>,
+    pub refresh_token: Option<String>,
+    pub scope: Option<String>,
+}
+
+impl Token {
+    /// Returns true if token is expired.
+    pub fn expired(&self) -> bool {
+        self.expires.map_or(false, |dt| dt < UTC::now())
+    }
+}