November 1, the day on which a Christian feast honoring all the saints is observed. Also called Allhallows. 1 November, when Christian churches remember all the saints. In Christianity, a day commemorating all the saints of the church, known and unknown. It is celebrated on November 1 in the Western churches and on the first Sunday after Pentecost in the Eastern churches. The first general observance of All Saints' Day was ordered by Pope Gregory IV in 837. In medieval England the festival was called All Hallows, and its eve is still known as Halloween