def _migrate_block_timetable_entry(self, old_entry):
        old_block = old_entry._LinkedTimeSchEntry__owner
        try:
            session = self.legacy_session_map[old_block.session]
        except KeyError:
            self.importer.print_warning(cformat('%{yellow!}Found zombie session {}').format(old_block.session),
                                        event_id=self.event.id)
            session = self._migrate_session(old_block.session)
        session_block = SessionBlock(session=session, title=convert_to_unicode(old_block.title),
                                     duration=old_block.duration)
        session_block.timetable_entry = TimetableEntry(event_new=self.event, start_dt=old_block.startDate)
        if session.legacy_mapping is not None:
            session_block.legacy_mapping = LegacySessionBlockMapping(event_new=self.event,
                                                                     legacy_session_id=old_block.session.id,
                                                                     legacy_session_block_id=old_block.id)
        self._migrate_location(old_block, session_block)
        session_block.person_links = list(self._migrate_session_block_person_links(old_block))
        self._migrate_timetable_entries(old_block._schedule._entries, session_block)
        return session_block.timetable_entry