December 26 is the feast of Stephen.
Sometimes the date of their death is the feast day but it is not the rule. It can be on almost any day of the year. Actually, the Church does not call it the date of death but the date the person was reborn into Heaven.
Sometimes the feast day is the memorial of the date when the person died, or was reborn into Heaven. Sometimes it is another important date in the life of the person, such as the feast day of John Neumann which is the anniversary of the date he converted to Catholicism. Other times it is a date picked, more or less, in random.
The feast day of St. Nicholas of Myra is December 6.
April 16 is the feast of St. Bernadette.
A Saint's feast day falls on whatever day was chosen by the church. It could be a date that has significance to the Saint or a random day.
Rarely. It is frequently the date of their entry into Heaven (date of death) but it can be any date.
Sometimes a feast day of a saint is on or near their death day. Since we do not know the date of death of Saint Jude, there may be no significance to the date.
The feast day of a saint can be any random date or it may fall on the commemoration day of some event of the saint's life, such as their date of death, the day of their canonization or other such event.
May 1st is the feast of St. Joseph the Worker. He also has a feast day on March 19.
Oscar Romero has not yet been beatified so does not have a feast day.
jan. 28, the same date he died..