All Saints’ Day (Solemnity of All Saints, All Hallows, Hallowmas or All Saints’)is celebrated on 1 November by most Western Christians and is to honor all saints known and unknown. In some Catholic countries, it is a holiday. It is a holy day of obligation for most Catholics except when it falls on a Saturday or Monday. In that case it is celebrated on Sunday. Eastern Orthodox is celebrated on the first Sunday after Pentecost and is called All Saints’ Sunday.
Pope Boniface IV formally started All Saints’ Day on May 13, 609 AD. He also established All Souls’ Day to follow All Saints’ Day. Pope Gregory IV made 1 November All Saints’ Day followed by All Souls’ Day. The May 13 day was formally abandoned. In Ireland, All Saints’ Day was originally celebrated on April 20 to avoid being mixed with the pagan feasts revolving around Samhain on 1 November. It was moved later to 1 November and has been there ever since. All Saints’ Day is a public holiday in Ireland where all schools, businesses and government is closed.