Shakespeare's Birthday?

"On Being Questioned Where I Am Today, April 23"

In Andrews Hall: that’s where you'll find the man,
Reflecting on the likelihood this day
Was born to us a child who would be styled
“Sweet swan of Avon” in his after years.
Alas! We know not with firm certainty
When William Shakespeare truly shuffled on
This mortal coil – the parish records note
“Gulielmus” (William) was so christenéd,
The son of one “Johannes Shakspere” (John),
On April twenty-sixth; nativity
Into this solid flesh was no precise
Concern for either clerk or chronicle.
The later clerk, in Lincoln, Lancaster
(O Pioneers! with place names redolent
Of geographic Anglophilia),
Confesses that the twenty-third is but
A sensible conjecture, no plain fact
As far as when to celebrate Will’s day
In accents like the Bard’s and festivals
Of pomp, and triumph, and much reveling.
E’en so: By Harry, England, and Saint George
(Whose feast this fairly is) let us applaud
The inexhaustibility of Will,
Whose date of birth must needs remain, much like
His plays and poems, open to surmise.