All Saints' Day, also known as All Hallows, Day of All the Saints, Solemnity of All Saints, or Feast of All Saints is a solemnity celebrated on 1 November by the Roman Catholic Church of Latin rite and various Protestant denominations, and on the first Sunday after Pentecost in Eastern Catholicism and Eastern Orthodoxy, in honour of all the saints, known and unknown. The liturgical celebration begins at Vespers on the evening of 31 October and ends at the close of 1 November. It is thus the day before All Souls' Day.
Hallowmas is another term for the feast, and was used by Shakespeare in this sense...