Although convenient for modern celebrants, I've always disapproved of taking events associated with particular historic dates - including birthdays - and observing them whenever it's most convenient. I remember the outcry when this was attempted with Veteran's Day - formerly Armistice Day - which of course famously occurred on the eleventh hour of the eleventh day of the eleventh month of 1918. Today, probably nobody's left who would know the difference or significance of the date!