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Wednesday, Friday, and Saturday after Gaudete Sunday (3rd Sunday of Advent) are known as “Advent Embertide,” and they come near the beginning of the Season of Winter (December, January, February). Liturgically, the readings for the days’ Masses follow along with the general themes of Advent, opening up with Wednesday’s Introit of Isaias 45: 8 and Psalm 18:2 :
Drop down dew, ye heavens, from above, and let the clouds rain the Just:
let the earth be opened and bud forth a Savior. The heavens show forth the glory of God:
and the firmament declareth the work of His hands.
Wednesday’s and Saturday’s Masses will include one and four Lessons, respectively, with all of them concerning the words of the Prophet Isaias except for the last lesson on Saturday, which comes from Daniel and recounts how Sidrach, Misach, and Abdenago are saved from King Nabuchodonosor’s fiery furnace by an angel. This account, which is followed by a glorious hymn, is common to all Embertide Saturdays but for Whit Embertide. (1)
Four times a year, the Church sets aside three days to focus on God through His marvelous creation. These quarterly periods take place around the beginnings of the four natural seasons 1 that “like some virgins dancing in a circle, succeed one another with the happiest harmony,” as St. John Chrysostom wrote (see Readings below).
These four times are each kept on a successive Wednesday, Friday, and Saturday and are known as “Ember Days,” or Quatuor Tempora, in Latin. The first of these four times comes in Winter, after the the Feast of St. Lucy; the second comes in Spring, the week after Ash Wednesday; the third comes in Summer, after Pentecost Sunday; and the last comes in Autumn, after Holy Cross Day.
Their dates can be remembered by this old mnemonic:
Sant Crux, Lucia, Cineres, Charismata Dia
Ut sit in angaria quarta sequens feria.
Holy Cross, Lucy, Ash Wednesday, Pentecost,
are when the quarter holidays follow.