when did patient 62983 get the oxygen saturation lab test last time until 26 months ago?
select labevents.charttime from labevents where labevents.itemid in ( select d_labitems.itemid from d_labitems where d_labitems.label = 'oxygen saturation' ) and labevents.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 62983 ) and datetime(labevents.charttime) <= datetime(current_time,'-26 month') order by labevents.charttime desc limit 1