The Empire asked all the people to believe in Christianity
. A lot of pagan joined in the church and bring the pagan traditions in, as a result. As the church was not able to eliminate all the pagan traditions, some were consecrated, especially the dying festival on October 31st. In the 8th century, the Roman pope set November 1st as All Saints' Day so as to commemorate all the sacrificed devotee in history. Thus, October 31st is the eve before Halloween