The example for date_time_html suggests that whatever format I specify in date_format, this octopress plugin will parse that format and create a html with a correctly classed span for each element.
That isn't the case however. As soon as I define in _octopress.yml
the generated code looks like this
<time class='entry-date' datetime='2014-08-13T00:17:32+02:00'>
<span class='date'>13-Aug-2014</span>
<span class='time'>12:17 am</span>
</time>
I actually prefer it that way, but others might be surprised by this.