when did patient 23929 receive a lab test in 08/last year last time?
select labevents.charttime from labevents where labevents.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 23929 ) and datetime(labevents.charttime,'start of year') = datetime(current_time,'start of year','-1 year') and strftime('%m',labevents.charttime) = '08' order by labevents.charttime desc limit 1