Since ancient times, Christians have used the Christian calendar (also called the liturgical year) to orient themselves to the two most significant seasons in the yearly Christian cycle of time: Christmas and Easter. Within such a calendar, every day has a vital and traditionally sacred place relative to the life, ministry, death and resurrection of Christ.
Because the Christian year is rooted in the liturgical observances of ancient Judaism, it should not surprise us that over time different strains of Christianity developed different variations on the Christian year. Typically, though, the Protestant church year runs as follows.
The Advent-Christmas-Epiphany Cycle
Advent -- Rather than on Jan. 1, the Christian new year begins on the Sunday that falls nearest Nov. 30, which this year is on Nov. 28. That Sunday through the next three Sundays --- in other words, the time encompassing the four Sundays before Christmas -- is known as the season of Advent (which is Latin for "coming"). During this time the church, liturgically, spiritually and practically, prepares for the glory of Christmas day.
Christmas -- While Christmas Day is celebrated on Dec. 25, the Christmas season lasts the 12 days from Dec. 25 to the Feast of the Epiphany on Jan. 6. (This is where the "12 Days of Christmas" comes from.)
Epiphany -- Epiphany is Greek for "manifestation," "show," "revealed." During this season Christians focus on God manifesting as Jesus, on his sacrifice and the atonement. It is also a time when churches tend to focus on their missional work: If Jesus gave his all to save believers, then believers must give their all to save others. Epiphany runs from the close of Christmastide (a traditional word for the Christmas season) on Jan. 6 to the beginning of Lent (see below).
Ordinary Time -- This does not mean "boring time where nothing interesting happens." The term derives from the word "ordinal," as in "numbered." And, indeed, the Sundays that fall within Ordinary Time are often designated in such ways as The Third Sunday After Pentecost, or The Second Sunday Before Lent. Ordinary Time refers to any period of time that falls outside the major seasons of the liturgical year. Where within the times of Christmas and Easter we focus on specific aspects of Christ's life and meaning to us, during Ordinary Time we think about what Christ means to the entirety of our lives. It is, after all, during the "ordinary times" of our life that Christ can, and should, mean as much to us as he does at any other.
The Easter Cycle
Lent -- A 40-day period (based on the 40 days of temptation that Jesus faced in the wilderness) of fasting, prayer, self-examination and repentance, in anticipation of the day Christ sacrificed himself in atonement for the sins of all mankind.
Holy Week -- Sometimes called Passion Week, because of the awesome and terrible events that unfolded between the days of Palm Sunday (when Jesus triumphantly rode into Jerusalem on the back of a donkey) and Holy Saturday (when Jesus was buried after his passion and crucifixion on Good Friday).
Easter -- Yay! Easter is the most important, most ancient festival of the Christian church year. Every Sunday of the Easter season, which lasts 50 days overall, is a celebration of the glorious resurrection of Jesus Christ. He is, as they say, risen indeed.
Pentecost -- This day celebrates the occasion of the Holy Spirit first descending upon Christ's disciples. Pentecost is the last day of the Easter season, meaning it falls on the 50th day after Easter. Pentecost Sunday is a traditional day for baptism and the confirmation of new Christians.
Ordinary Time -- From the day of Pentecost to the First Sunday of Advent.
Within the Christian liturgical calendar are of course a great many significant days. Ash Wednesday (the first of the forty days of Lent), the Baptism of the Lord (usually celebrated on the first Sunday after the Epiphany), and Trinity Sunday (the first Sunday after Pentecost when we celebrate the Trinity) are but three such days.