Django template filters are like unix pipes. In this example, we want to create a filter that take a $Date$ Subversion keyword and modify the date and time string format. Note: that also work with CVS, because CVS and Subversion shares the same keyword syntax.

Create a templatetags directory in you application folder, touch a __init_.py and a file where you are going to write your filters, for this example svn_keyword_filters.py

You should have a directory tree looking like:

myapp/
    views.py
    templatetags/
        __init__.py
        svn_keyword_filters.py

In svn_keyword_filters.py write:

from django import template
register = template.Library()
 
@register.filter("svndate")
def svndate(value):
    return value[7:26]

In the template add something like:

<p>
  {% load svn_keyword_filters  %}
  {{ "$Date: 2006-11-02 11:45:14 +0100 (Thu, 02 Nov 2006) $"|svndate }}
</p>

Produces this html output

<p>
  2006-11-02 11:45:14
</p>

Check the Django documentation about custom template filters.