def unmarshal(self, v):
        """
        Convert a timestamp in "2012-12-13T03:43:19Z" format to a `datetime.datetime` object.
        """
        if not isinstance(v, datetime):
            if isinstance(v, six.integer_types):
                v = arrow.get(v)
            else:
                try:
                    # Most dates are in this format 2012-12-13T03:43:19Z
                    v = datetime.strptime(v, "%Y-%m-%dT%H:%M:%SZ")
                except ValueError:
                    # ... but not all.
                    v = arrow.get(v).datetime
            # Translate to specified TZ
            v = v.replace(tzinfo=self.tzinfo)

        return v
Convert a timestamp in "2012-12-13T03:43:19Z" format to a `datetime.datetime` object.