It’s not just a coincidence, says Stephen Nichols. And he’s basically right, though he seems to have confused All Saints Day (Hallowmass) with All Souls Day. All Saints falls on November 1; All Souls usually falls on November 2. Halloween is simply All Hallow’s Eve, or the evening before All Saints (Hallows) Day.
But why did Luther post his 95 theses on Halloween? Here’s the nub of Nichols’ answer, but you’ll want to read the rest.
On November 1, 1517, a massive exhibit of newly acquired relics would be on display at Wittenberg, Luther’s home city. Pilgrims would come from all over, genuflect before the relics, and take hundreds, if not thousands, of years off time in purgatory. Luther’s soul grew even more vexed. None of this seemed right.