Walpurga 's feast day is on 25 February , but the day of her canonization , 1 May ( possibly in AD 870 ) , was also celebrated during the high medieval period , especially in the 11th century under Anno II , Archbishop of Cologne , so that Walpurgis Night is the eve of May Day , celebrated in continental folklore with dancing .
Walpurga 's feast day is on 25 February .