Add docs for timezone setting.

site/_posts/2012-07-01-configuration.md

@@ -81,6 +81,21 @@ class="flag">flags</code> (specified on the command-line) that control them.
         <p><code class="option">include: [DIR, FILE, ...]</code></p>
       </td>
     </tr>
+    <tr class='setting'>
+      <td>
+        <p class='name'><strong>Time Zone</strong></p>
+        <p class="description">
+            Set the time zone for site generation. This sets the <code>TZ</code>
+            shell environment variable, which Ruby uses to handle time and date
+            creation and manipulation. Any entry from the
+            <a href="http://en.wikipedia.org/wiki/Tz_database">IANA Time Zone
+            Database</a> is valid.
+        </p>
+      </td>
+      <td class='align-center'>
+        <p><code class="option">timezone: TIMEZONE</code></p>
+      </td>
+    </tr>
   </tbody>
 </table>