Walpurgis heralds May Day, Samhain heralds All Saints Day.
They are opposite ends of the season. One is spring planting and the other is fall harvest.
And of course April 30 is the time the devil asks for his due; (from my blog post last year.)
It’s possible that I shall make an ass of myself. But in that case one can always get out of it with a little dialectic. I have, of course, so worded my proposition as to be right either way (K.Marx, Letter to F.Engels on the Indian Mutiny)