instruction: what was the last time since 4 years ago that patient 027-188709 went to the hospital via an emergency department?
response: SELECT patient.hospitaladmittime FROM patient WHERE patient.uniquepid = '027-188709' AND patient.hospitaladmitsource = 'emergency department' AND DATETIME(patient.hospitaladmittime) >= DATETIME(CURRENT_TIME(), '-4 year') ORDER BY patient.hospitaladmittime DESC LIMIT 1