vendor.modification_time.strftime('%H:%M / %d %b %Y')
so that vaguely works, but i've been unable to find a decent list of all the possible formatting characters that work in whatever frankenstein jinja-django-python monster we've got running on the site. Not all of the django ones work (http://docs.djangoproject.com/en/dev/ref/templates/builtins/).
Pattern matching seems to indicate that you can format jinja datetime / timestamps using python date formatting ...