December 1
There are a number of saints and blesseds named Edmund. If you are referring to Saint Osmund (also known as Edmund) who became Bishop of Salisbury, England in 1078, his feast day is December 4.
Because that is the day when Saint Edmund (also called St. Edmund Rich or St. Edmund of Abingdon) is said to have died. The confusion is that there are two saints named Edmund. The one you are asking about was also Archbishop of Canterbury. He was born on November 20, 1180, which was the feast of the other Edmund, St. Edmund King and Martyr. But they are not the same person, and their feast days are on different days-- St. Edmund the Martyr's in observed on the 20th of November, while St. Edmund of Abingdon has his feast day on November 16.
Pope Benedict I is not a saint and has no feast day.
Saint Maria Goretti's Feast Day is July 6th.
Saint Christopher's feast day is July 25th.
Saint Laura's Feast Day is October the 19th.
The 23rd of April is the feast day of Saint George.
Saint Helena's feast day is August 18.
The feast day of saint Mark is April 25.
November 22 is the feast day of Saint Cecilia.
August 11 is the feast day of Saint Philomena.
July 24 is the feast day of Saint Charbel.