title: Nginx Caching issue with Expires Header
body: <p>We are using Nginx as a reverse proxy and everything seems to work fine.We have caching enabled and this was working fine from Nov 15 to Nov 30. The proxied server returns a request which has expires header set to expire after 5 mins. 
  However this stopped working on Dec 1. And the culprit seems to be the date format. 
  With a simple test case we were able to figure out that :</p>
  
  <pre><code> new org.mockserver.model.Header("Expires", "Tue, 04 Dec 2018 16:23:31 GMT")
  </code></pre>
  
  <p>Works fine. However this fails:</p>
  
  <pre><code> new org.mockserver.model.Header("Expires", "Tue, 4 Dec 2018 16:23:31 GMT")
  </code></pre>
  
  <p>The following are my proxy settings:</p>
  
  <pre><code>proxy_cache_path /var/cache/nginx levels=1:2 keys_zone=nginx_cache:10m max_size=10g use_temp_path=off;
  
  proxy_cache nginx_cache;
  proxy_cache_methods GET;
  proxy_ignore_headers Set-Cookie;
  </code></pre>
  
  <p>Is it a problem with my configuration or is it a issue with Nginx ? This was issue we tried in bot Nginx version 1.3.7 and 1.3.10</p>
  
  <p><strong>EDITED</strong>
  These headers were sent from a thirdparty API. However they seem to be also sending other headers (example form test case):</p>
  
  <pre><code>        new org.mockserver.model.Header("Date", "Tue, 04 Dec 2018 16:13:45 GMT"),
          new org.mockserver.model.Header("Expires", "Tue, 6 Dec 2018 16:23:31 GMT"),
          new org.mockserver.model.Header("Cache-Control", "max-age=586, must-revalidate")
  </code></pre>
  
  <p>and as per this link, the cache-control should have had precedence :
  <a href="https://stackoverflow.com/questions/5799906/what-s-the-difference-between-expires-and-cache-control-headers">what’s the difference between Expires and Cache-Control headers?</a></p>
  
  <p>But nginx somehow seems to fail on the expires header.</p>