All Saints' Day is a solemn holy day of the Catholic Church celebrated annually on November 1. The day is dedicated to the saints of the Church, that is, all those who have attained heaven. It should not be confused with All Souls' Day, which is observed on November 2, and is dedicated to those who have died and not yet reached heaven.
All Saints' Day was formally started by Pope Boniface IV, who consecrated the Pantheon at Rome to the Virgin Mary and all the Martyrs on May 13 in 609 AD. Boniface IV also established All Souls' Day, which follows All Saints.