title: Why is jekyll --server returning errors
body: <p>I've noticed a couple of posts that are similar to this but don't understand how to solve the issue.</p>
  
  <p>I have rbenv with ruby 1.9.3-p392 installed and get the following error when I run jekyll --server:</p>
  
  <pre><code>Configuration from /Users/seiju/Sites/a8os/_config.yml
  Building site: /Users/seiju/Sites/a8os -&gt; /Users/seiju/Sites/a8os/_site
  Liquid Exception: undefined method `xmlschema' for nil:NilClass in sitemap.xml
  /Users/seiju/.rbenv/versions/1.9.3-p392/lib/ruby/gems/1.9.1/gems/jekyll-0.12.1/lib/jekyll/filters.rb:57:in `date_to_xmlschema'
  /Users/seiju/.rbenv/versions/1.9.3-p392/lib/ruby/gems/1.9.1/gems/liquid-2.5.0/lib/liquid/strainer.rb:43:in `invoke'
  /Users/seiju/.rbenv/versions/1.9.3-p392/lib/ruby/gems/1.9.1/gems/liquid-2.5.0/lib/liquid/context.rb:75:in `invoke'
  /Users/seiju/.rbenv/versions/1.9.3-p392/lib/ruby/gems/1.9.1/gems/liquid-2.5.0/lib/liquid/variable.rb:50:in `block in render'
  /Users/seiju/.rbenv/versions/1.9.3-p392/lib/ruby/gems/1.9.1/gems/liquid-2.5.0/lib/liquid/variable.rb:38:in `each'
  /Users/seiju/.rbenv/versions/1.9.3-p392/lib/ruby/gems/1.9.1/gems/liquid-2.5.0/lib/liquid/variable.rb:38:in `inject'
  /Users/seiju/.rbenv/versions/1.9.3-p392/lib/ruby/gems/1.9.1/gems/liquid-2.5.0/lib/liquid/variable.rb:38:in `render'
  /Users/seiju/.rbenv/versions/1.9.3-p392/lib/ruby/gems/1.9.1/gems/liquid-2.5.0/lib/liquid/block.rb:106:in `block in render_all'
  /Users/seiju/.rbenv/versions/1.9.3-p392/lib/ruby/gems/1.9.1/gems/liquid-2.5.0/lib/liquid/block.rb:93:in `each'
  /Users/seiju/.rbenv/versions/1.9.3-p392/lib/ruby/gems/1.9.1/gems/liquid-2.5.0/lib/liquid/block.rb:93:in `render_all'
  /Users/seiju/.rbenv/versions/1.9.3-p392/lib/ruby/gems/1.9.1/gems/liquid-2.5.0/lib/liquid/block.rb:82:in `render'
  /Users/seiju/.rbenv/versions/1.9.3-p392/lib/ruby/gems/1.9.1/gems/liquid-2.5.0/lib/liquid/template.rb:124:in `render'
  /Users/seiju/.rbenv/versions/1.9.3-p392/lib/ruby/gems/1.9.1/gems/liquid-2.5.0/lib/liquid/template.rb:132:in `render!'
  /Users/seiju/.rbenv/versions/1.9.3-p392/lib/ruby/gems/1.9.1/gems/jekyll-0.12.1/lib/jekyll/convertible.rb:79:in `do_layout'
  /Users/seiju/.rbenv/versions/1.9.3-p392/lib/ruby/gems/1.9.1/gems/jekyll-0.12.1/lib/jekyll/page.rb:100:in `render'
  /Users/seiju/.rbenv/versions/1.9.3-p392/lib/ruby/gems/1.9.1/gems/jekyll-0.12.1/lib/jekyll/site.rb:204:in `block in render'
  /Users/seiju/.rbenv/versions/1.9.3-p392/lib/ruby/gems/1.9.1/gems/jekyll-0.12.1/lib/jekyll/site.rb:203:in `each'
  /Users/seiju/.rbenv/versions/1.9.3-p392/lib/ruby/gems/1.9.1/gems/jekyll-0.12.1/lib/jekyll/site.rb:203:in `render'
  /Users/seiju/.rbenv/versions/1.9.3-p392/lib/ruby/gems/1.9.1/gems/jekyll-0.12.1/lib/jekyll/site.rb:41:in `process'
  /Users/seiju/.rbenv/versions/1.9.3-p392/lib/ruby/gems/1.9.1/gems/jekyll-0.12.1/bin/jekyll:264:in `&lt;top (required)&gt;'
  /Users/seiju/.rbenv/versions/1.9.3-p392/bin/jekyll:23:in `load'
  /Users/seiju/.rbenv/versions/1.9.3-p392/bin/jekyll:23:in `&lt;main&gt;'
  Build Failed
  </code></pre>
  
  <p>I'm so confused and don't know where to start on fixing this issue. I'm also using jekyll version (0.12.1).</p>
  
  <p>Below is my sitemap.xml:</p>
  
  <pre><code>---
  ---
  
  &lt;?xml version="1.0" encoding="UTF-8"?&gt;
  &lt;?xml-stylesheet type="text/xsl" href="/sitemap.xsl"?&gt;
  &lt;urlset xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.sitemaps.org/schemas/sitemap/0.9 http://www.sitemaps.org/schemas/sitemap/0.9/sitemap.xsd" xmlns="http://www.sitemaps.org/schemas/sitemap/0.9"&gt;    
  &lt;url&gt;
  &lt;loc&gt;http://aceeightofspades.com/&lt;/loc&gt;
  &lt;lastmod&gt;{{ site.time | date_to_xmlschema }}&lt;/lastmod&gt;
  &lt;changefreq&gt;daily&lt;/changefreq&gt;
  &lt;priority&gt;1.0&lt;/priority&gt;
  &lt;/url&gt;
  &lt;url&gt;
  &lt;loc&gt;http://aceeightofspades.com{{ post.url }}/&lt;/loc&gt;
  &lt;lastmod&gt;{{ post.date | date_to_xmlschema }}&lt;/lastmod&gt;
  &lt;changefreq&gt;weekly&lt;/changefreq&gt;
  &lt;priority&gt;0.8&lt;/priority&gt;
  &lt;/url&gt;
  &lt;/urlset&gt;
  </code></pre>