The feast of St. Hilda of Whitby is observed by the Greek Orthodox Church,  the Anglican Church,  and the Roman Catholic Church. 
"Christ's servant Abbess Hilda, whom all her acquaintances called Mother because of her wonderful devotion and grace, was not only an example of holy life to members of her own community; for she also brought about the amendment and salvation of many living at a distance, who heard the inspiring story of her industry and goodness."
-- Venerable Bede 
Hilda  hosted the Synod of Whitby.  Two of the major issues discussed at the synod were the setting of the date of Easter and the tonsure of monks.
(The Roman tonsure left a circle of hair around a bald spot. The Celtic tonsure left the hair behind a line drawn from ear to ear. Both styles may be seen in the picture.)
Mother Hilda encouraged Caedmon  the cowherd to become a monk and to continue writing poetry in the vernacular.
Hwæt, ic swefna cyst secgan wylle,
hwæt m? gemætte to midre nihte,
syðþan reordberend reste wunedon.
þ?hte m? þæt ic ges?we syllicre tr?ow
on lyft lædan l?ohte bewunden,
-- Caedmon