title: Alternative to colon in a time format
body: <p>ISO 8601 recommends the following format for a date and time:</p>
  
  <pre><code>2014-12-29T16:11:20+00:00
  </code></pre>
  
  <p>I'm rather fond of this format since it allows for lexical ordering. But there is a small problem: some file systems don't allow colons in file names (at least not normally). ISO 8601 does allow for omitting the colons, but I would rather have <em>some</em> symbol there than have the numbers run together:</p>
  
  <pre><code>2014-12-29T161120+0000
  </code></pre>
  
  <p>Does ISO 8601 allow for a symbol other than colons? I couldn't find any indication that it does. If not, is there another well recognized symbol I could use? (Perhaps another standard proposes such a symbol?)</p>