Mind you, keeping accurate records of anything is a fairly recent phenomenon.  That’s why no one can say with certainty when the Bard was born... until now.  Shakespeare was born on April 23, 1564.  That day may not be right, but we’re going to say it with certainty. 

The closest thing we have of any proof of when Shakespeare was born is his christening date, April 26, 1564.  In Shakespeare’s time, as laid out in The Book of Common Prayer (one I’m sure we’ve all read), “...it was required that a child be baptized on the nearest Sunday or holy day following the birth, unless the parents had a legitimate excuse.”  The nearest holy day after the 23rd (a Thursday), however, was the 25th, St. Mark’s day.  However, St. Mark’s day is still considered by some to be unlucky, and who wants to be christened on a day when “...the spirits of those doomed to die in that year...” are supposedly walking around in the churchyard?  So putting off his christening to the 26th (the Daily Double: St. George’s day and a Sunday) for fear of haunts would’ve been a pretty legitimate excuse.  (Mabillard)

Of course, he could’ve just as easily been born on the 24th or the 25th.  But, then, we do know that Shakespeare died on April 23rd (in 1616).  So having him born on the same day saves ink.  And that’s as good a reason as any.