when did patient 42473 first have the maximum mch - value in 12/this year?
select labevents.charttime from labevents where labevents.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 42473 ) and labevents.itemid in ( select d_labitems.itemid from d_labitems where d_labitems.label = 'mch' ) and datetime(labevents.charttime,'start of year') = datetime(current_time,'start of year','-0 year') and strftime('%m',labevents.charttime) = '12' order by labevents.valuenum desc, labevents.charttime asc limit 1