###HUMAN: when did patient 021-221706 come to the hospital for the last time until 4 years ago via an floor?, ###ASSISTANT: SELECT patient.hospitaladmittime FROM patient WHERE patient.uniquepid = '021-221706' AND patient.hospitaladmitsource = 'floor' AND DATETIME(patient.hospitaladmittime) <= DATETIME(CURRENT_TIME(), '-4 year') ORDER BY patient.hospitaladmittime DESC LIMIT 1