when did patient 21302 get admitted via transfer from hosp/extram to the hospital for the first time this year?
select admissions.admittime from admissions where admissions.subject_id = 21302 and admissions.admission_location = 'transfer from hosp/extram' and datetime(admissions.admittime,'start of year') = datetime(current_time,'start of year','-0 year') order by admissions.admittime asc limit 1