def changes_since(self, domain, date_or_datetime):
        """
        Gets the changes for a domain since the specified date/datetime.
        The date can be one of:
            - a Python datetime object
            - a Python date object
            - a string in the format 'YYYY-MM-YY HH:MM:SS'
            - a string in the format 'YYYY-MM-YY'

        It returns a list of dicts, whose keys depend on the specific change
        that was made. A simple example of such a change dict:

            {u'accountId': 000000,
             u'action': u'update',
             u'changeDetails': [{u'field': u'serial_number',
               u'newValue': u'1354038941',
               u'originalValue': u'1354038940'},
              {u'field': u'updated_at',
               u'newValue': u'Tue Nov 27 17:55:41 UTC 2012',
               u'originalValue': u'Tue Nov 27 17:55:40 UTC 2012'}],
             u'domain': u'example.com',
             u'targetId': 00000000,
             u'targetType': u'Domain'}
        """
        domain_id = utils.get_id(domain)
        dt = utils.iso_time_string(date_or_datetime, show_tzinfo=True)
        uri = "/domains/%s/changes?since=%s" % (domain_id, dt)
        resp, body = self._retry_get(uri)
        return body.get("changes", [])