instruction: what was the last time patient 021-25705 has had the minimum sao2 on 06/03/this year?
response: SELECT vitalperiodic.observationtime FROM vitalperiodic WHERE vitalperiodic.patientunitstayid IN (SELECT patient.patientunitstayid FROM patient WHERE patient.patienthealthsystemstayid IN (SELECT patient.patienthealthsystemstayid FROM patient WHERE patient.uniquepid = '021-25705')) AND NOT vitalperiodic.sao2 IS NULL AND DATETIME(vitalperiodic.observationtime, 'start of year') = DATETIME(CURRENT_TIME(), 'start of year', '-0 year') AND STRFTIME('%m-%d', vitalperiodic.observationtime) = '06-03' ORDER BY vitalperiodic.sao2, vitalperiodic.observationtime DESC LIMIT 1