
In the next century, Pope Gregory III changed the day to November 1 when he dedicated a chapel in St. Peter’s Basilica to the saints. Yet another century later, Pope Gregory IV added All Saints Day to the Christian calendar, extending the celebration from Rome to churches everywhere. With All Saints Day came All Hallows' Eve on October 31. This was, perhaps, an effort to offset the pagan celebration of Samhain with a religious celebration.