November 1st marks the second day of Allhallowtide known as All Saints Day (October 31st is All Hallow’s Eve and November 2nd is All Souls Day) and is a festival recognized by many Christian denominations as a day to remember and honor those who have attained sainthood.
There is some debate, speculation and controversy over what relationship All Saints Day has with the ancient Celtic festival of Samhain. Some believe that All Saints Day was positioned on the calendar as a means to merge it with Samhain and thus aid in the conversion of the Celts to Christianity.
Others, however, believe that the two holidays developed independent from one another and have only been merged through their celebrations and traditions that have come down through the ages and melded into other cultures.
Today, All Saints Day is celebrated by many Christians denominations and throughout many parts of Europe, Central America and Mexico (where it is part of the Day of the Dead festivities.)
More information can be found here: https://en.wikipedia.org/wiki/All_Saints%27_Day