The Presentation of the Blessed Virgin Mary (as it is known in the West), or The Entry of the Most Holy Theotokos into the Temple (its name in the East), is a liturgical feast celebrated on November 21 by the Roman Catholic, Eastern Catholic, and Orthodox Churches.
The feast is associated with an event recounted not in the New Testament, but in the apocryphal Infancy Narrative of James.
According to that text, Mary’s parents, Joachim and Anne, who had been childless, received a heavenly message that they would have a child.
In thanksgiving for the gift of their daughter, they brought her, when still a child, to the Temple in Jerusalem to consecrate her to God.
Later versions of the story (such as the Gospel of Pseudo-Matthew and the Gospel of the Nativity of Mary) tell us that Mary was taken to the Temple at around the age of three in fulfillment of a vow.
Tradition held that she was to remain there to be educated in preparation for her role as Mother of God.
In Eastern Orthodox tradition, this is one of the days when women named Mary (Μαρία in Greek) and Despoina (Δέσποινα in Greek) celebrate their Name Day.
The Eastern Orthodox Church celebrates it on November 21 as one of its twelve Great Feasts.
For those churches which follow the Julian Calendar, November 21 falls on December 4 of the modern Gregorian Calendar.
In the Orthodox Church the feast always falls during the Nativity Fast, and on the day of the feast the fasting rules are lessened somewhat so that fish, wine, and oil may be eaten.
For the Roman Catholic Church, on the day of the Presentation of the Blessed Virgin Mary, “we celebrate that dedication of herself which Mary made to God from her very childhood under the inspiration of the Holy Spirit who filled her with grace … .”
In the 1974 encyclical Marialis Cultus, Pope Paul VI wrote that “despite its apocryphal content, it presents lofty and exemplary values and carries on the venerable traditions having their origins in the Eastern churches”.
The three feasts of the Birthday of Our Lady, the Holy Name of Mary, and her Presentation in the Temple correspond in the Marian cycle with the first three feasts of the cycle of feasts of Jesus: namely, Christmas, the Holy Name of Jesus, and His Presentation at the Temple.
November 21 is also a “Pro Orantibus” Day, a day of prayer for cloistered religious “totally dedicated to God in prayer, silence, and concealment”.
with info from wikipedia.org