In the 7th century the Roman Empire had begun to dissipate but in its stead Christianity had spread throughout the western world. It is believed that during this period Pope Boniface IV designated May 13th as All Saints Day, a day much like Samhain, dedicated to honouring the dead. However, despite the introduction of the new holiday the Celt’s were still unwilling to give up Samhain.
In 739 A.D pope Gregory III came to power and set about amalgamating the two holidays together. He moved the date of All Saint’s day to November 1st so that it would conflict directly with Samhain. All Saint’s day was then preceded by All Soul’s day on the 2nd of November which is a Christian day of honouring the dead.
Rather than stripping the holiday of its roots altogether Pope Gregory decided to take the traditions of Samhain and adapt them to the Christian faith. Now you would no longer leave food out for ghost and ghouls so they wouldn’t pay tricks on you (modern day trick or treating) but instead you would exchange treats “soul cakes” with those less fortunate in exchange for prayers for dead relatives and friends.
Large parades and festivals were held on the day and those attending were actively encouraged to wear the costumes of deceased Saints. As time progressed so too did the holiday’s name, changing from Hallowmas to as we know it today Halloween. In its early days this holiday was celebrated similarly to Samhain with bonfires, costumes and large parades.