Traditionally it was December 4th, but her feast day has been removed from the Liturgical calendar in the Roman Rite because there isn't any evidence of her being a real person.
Her feast day was on December 4 but her feast was removed from the calendar and her cult suppressed in 1969.
It was founded on December 4th, 1786, which is the feast day for Saint Barbara.
Pope Benedict I is not a saint and has no feast day.
Saint Maria Goretti's Feast Day is July 6th.
The feast day of saint Mark is April 25.
Saint Christopher's feast day is July 25th.
Saint Laura's Feast Day is October the 19th.
July 24 is the feast day of Saint Charbel.
The 23rd of April is the feast day of Saint George.
Saint Helena's feast day is August 18.
August 11 is the feast day of Saint Philomena.
November 22 is the feast day of Saint Cecilia.