Feast Days of the Blesseds and Saints are usually marked on the day they died. The Feast Day of Blessed John Henry Newman , despite the fact he died on August 11 1890, is celebrated on October 9th, the day he converted to the Catholic Church.
Here is a letter penned on that very day.
Littlemore, October 9. 1845
My Dear Madam,
I have not been able to tell you. I shall, please God, be received this evening. Father Dominic, the Passionist, who is hearing my confession, did not come till late last night, and has to get away soon, being on his way to Belgium. So he fixed this evening.
I am so engaged, in various ways, as you may suppose, that I merely tell you this, thanking you sincerely for all the interest you feel in me, and earnestly praying & trusting that it will not be found misplaced. The Church of Rome has never acknowledged English Orders, though she has never formally denied them. Practically, I am a layman in her eyes.
Yours very sincerely,
John H Newman