when was the last time that patient 88254 had the maximum white blood cells value?
select labevents.charttime from labevents where labevents.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 88254 ) and labevents.itemid in ( select d_labitems.itemid from d_labitems where d_labitems.label = 'white blood cells' ) order by labevents.valuenum desc, labevents.charttime desc limit 1