when did patient 73075 first have a laboratory test in 12/2104?
select labevents.charttime from labevents where labevents.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 73075 ) and strftime('%y-%m',labevents.charttime) = '2104-12' order by labevents.charttime asc limit 1