The calendar of saints is a traditional Christian method of organizing a liturgical year by associating each day with one or more saints and referring to the feast day of said saint. The system arose from the early Christian custom of annual commemoration of martyrs on the dates of their deaths, or birth into heaven, and is thus referred to in Latin as dies natalis ("day of birth"). In the Eastern Orthodox Church, it is called a Menologion. Menologion may also refer to a set of icons on which saints are depicted along the order of dates of their feasts, often made in two panels.

As the number of recognized saints increased during Late Antiquity and the first half of the Middle Ages, eventually every day of the year had at least one saint who was commemorated on that date. To deal with this increase, some saints were moved to alternate days in some traditions or completely removed, with the result that some saints have different feast days in different calendars. For example, Ss. Perpetua and Felicity died on 7 March, but this date was later assigned to St. Thomas Aquinas, allowing them only a commemoration (see Tridentine Calendar), so in 1908 they were moved one day earlier. When the 1969 reform of the Catholic calendar moved him to 28 January, they were moved back to 7 March (see General Roman Calendar). Both days can thus be said to be their feast day, in different traditions. The Roman Catholic calendars of saints in their various forms, which list those saints celebrated in the entire church, contains only a selection of the saints for each of its days. A fuller list is found in the Roman Martyrology, and some of the saints there may be celebrated locally.

John the Evangelist (יוחנן Standard Hebrew Yoḥanan, Tiberian Hebrew Yôḥānān meaning "Yahweh is gracious", Greek: Εὐαγγελιστής Ἰωάννης) (c. AD 1 - c. 100)^{[citation needed][dubious – discuss]} is the conventional name for the author of the Gospel of John. Traditionally he has been identified with the author of the other Johannine works in the New Testament – the three Epistles of John and the Book of Revelation, written by a John of Patmos – as well as with John the Apostle and the Beloved Disciple mentioned in the Gospel of John. However, at least some of these connections have been debated since about 200.

The Gospel of John refers to an unnamed "Beloved Disciple" of Jesus who bore witness to the gospel's message. The composer of the Gospel of John seemed interested in maintaining the internal anonymity of the author's identity.

The apostle John was a historical figure, one of the "pillars" of the Jerusalem church after Jesus' death. Some scholars believe that John was martyred along with his brother (Acts 12:1-2), although many other scholars doubt this. Harris believes that the tradition that John lived to old age in Ephesus developed in the late 2nd century, although the tradition does appear in the last chapter of the gospel. By the late 2nd century, the tradition was held by most Christians.

Mary Magdalene (original Greek Μαρία ἡ Μαγδαληνή), or Mary of Magdala, was one of Jesus' most celebrated disciples, and the most important female disciple in the movement of Jesus. Jesus cleansed her of "seven demons", ^{[Lu 8:2] [Mk 16:9]} sometimes interpreted as referring to complex illnesses. She became Jesus' close friend and most prominent during his last days, being present at the cross after the male disciples (excepting John the Beloved) had fled, and at his burial. She was the first person to see Jesus after his Resurrection, according to both John 20 and Mark 16:9.

Mary Magdalene is considered by the Catholic, Orthodox, Anglican, and Lutheran churches to be a saint, with a feast day of July 22. The Eastern Orthodox churches also commemorate her on the Sunday of the Myrrhbearers.

Consistently in the four Gospels, Mary Magdalene seems to be distinguished from other women named Mary by adding "Magdalene" (η Μαγδαληνή) to her name. Traditionally, this has been interpreted to mean that she was from Magdala, a town thought to have been on the western shore of the Sea of Galilee. Luke 8:2 says that she was actually "called Magdalene." In Hebrew מגדל Migdal means "tower", "fortress"; in Aramaic, "Magdala" means "tower" or "elevated, great, magnificent".