title: Check if accesstoken is expired Facebook SDK 4.7 ios
body: <p>I am using facebook sdk 4.7 and I need to check if accesstoken is expired.</p>
  
  <pre><code>FBSDKAccessToken *access_token = [FBSDKAccessToken currentAccessToken];
      if (access_token != nil) {
          //user is not logged in
  
          //How to Check if access token is expired?
          if ([access_token isExpired]) {
              //access token is expired ......
              //
          }
      }
  </code></pre>
  
  <p>And if I success with that I have to log the user again.</p>
  
  <p>The SDK gives an expiration_date.how can that help? The device may have wrong date.</p>