All Saints' Day is a solemn holy day of the Catholic Church celebrated annually normally on November 1. The day is dedicated to the saints of the Church, that is, all those who have attained heaven.
Although millions, or even billions of people may already be saints, All Saints' Day observances tend to focus on known saints --that is those recognised in the canon of the saints by the Catholic Church.
All Saints' Day is also commemorated by members of the Eastern Orthodox Church as well as some protestant churches, such as Lutheran and Anglican churches.
In normal times, All Saints' Day is a Catholic Holy Day of Obligation, meaning all Catholics are required to attend Mass on that day, unless they have an excellent excuse, such as serious illness.
Other countries have different rules according to their national bishop's conferences. The bishops of each conference have the authority to amend the rules surrounding the obligation of the day.
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.