Displaying updated date for entry I want to display the date an entry has been updated if it is later than the post date. So I've tried this:
   {% if entry.dateUpdated &gt;= entry.post %}
      Updated on {{ entry.dateUpdated.format('j M y') }}
   {% endif %}

But the date updated displays even if it is earlier. Is this because the date is not strictly a value as such?
Date fields in Craft are returned as DateTime objects, so you need to convert these to a string to be able to compare them.
The best way of doing this is to use the yyyy-mm-dd format as this makes it is easy to compare dates.
So your comparison would become:
   {% if (entry.dateUpdated|date('Y-m-d')) &gt;= (entry.postDate|date('Y-m-d')) %}
      Updated on {{ entry.dateUpdated.format('j M y') }}
   {% endif %}