ineed avice about chestnuts

i went to Morrison's and payed for some chestnuts last week the date said the 4th December and i wont to cook them its the 5th today i kept them out on kitchen counter all week are they safe to eat and cook still? if yes chestnuts are safe to eat how long do i keep them in oven for to cook them . i have never cooked chest nuts before so i have no way to compere notes to how i cook chestnuts.