The feast day of the saint is the same as the saint's day. For example, the Feast of St. Patrick is also known as St. Patrick's Day - March 17.
All saints and blesseds are assigned a feast day by the Vatican's Sacred Congregation for the Causes of Saints.
The feast of Saints Peter and Paul - June 29.
No. It can be any date but is usually the anniversary date of the death of the saint.
The feast of All Saints is celebrated on November 1st. It is a day for Christians to honor and remember all the saints in heaven, both known and unknown.
Everyday there are dozens of saints that are memorialized. However, if that feast falls on a Sunday or another important feast day, or Good Friday, the saint's day is not observed.
No. There are thousands of saints, so it would be impossible for every single one of them to have their own feast day (unless we decided to devote each day of the calendar to several different saints). Instead, only those saints who had the greatest impact on the Church or around whom a fervent devotion has grown are celebrated with feast days in the liturgical calendar.
Originally, the feast date of Thomas Aquinas was on March 7, the day he entered heaven. It is unknown to me the reason for the change. You need to know that there are thousands and thousands of saints and each one has a specific feast day. That means that, on any given day, there may be dozens of saints who are celebrated that same day.
June 29 - the feast of Saints Peter and Paul
Nearly all the recognized saints have a designated feast day each year. However, there are thousands and thousands of saints in Heaven whose names are known only to God who do not have a feast day. All Saints Day recognizes all the unnamed saints.
November 1 is the feast of All Saints.
The feast day of St. Cyril, brother of St. Methodius, is February 14. He shares the date with St. Valentine and several other saints.
Not necessarily. While it is normal to make a feast day the day of the year when a person is "reborn" into heaven, it is not a requirement. This is especially true with many of the ancient saints where no records remain of the date the person died. The feast day can be set for any day of the year.