From Help For Shepherds
The Lectionary is a traditional way of preaching through nearly the entire Bible in a three year period. For each Sunday there are four readings, OT, Psalms, Gospel, and Epistle. Over the three years the majority of the Bible is covered, especially of the New Testament. It is one of the few things that can unify what is preached across church lines as everyone joins in and preaches from the same passages. Besides that, the lectionary also emphasizes many of the Christian holidays that are mostly ignored now.
The page is divided up into seasons of the church year, with readings for all three years of the cycle. The seasons of the year are in chronological order.
Advent - Advent is the beginning of the Christian year, the start of the lectionary and is about the anticipation of the Jesus' birth before Christmas.
Christmas - While we normally associate Advent with Christmas, that is only the preperation, these are the readings for the celebration at and after Christmas.
Epiphany - Epiphany is the celebration of the Magi coming to Jesus, where God is revealed to the world. Epiphany is celebrated on Januray 6th every year, and these readings begin the next Sunday.
Lent - Lent is the time before Easter where Christians traditionally prepare for Jesus' sacrifice by giving up something ourselves as remembrance.
Easter - Easter begins this season of celebration, which runs until Pentecost.
Common Year - The common year runs from after Pentecost until the beginning of Advent. This is a very variable time length.
The 3 Year Cycle
The lectionary cycles through every three years, with a new lectionary year beginning with the start of Advent, not with the start of a new year. To figure out what year you are in, check below.
This year in the cycle concentrates on Gospel readings for Matthew. During the common year, Year B also deals with the later part of Genesis, Exodus, Numbers, Deuteronomy, Ruth, Philippians, Romans, and 1 Thessalonians.
Year A is used for: 2004/2005, 2007/2008, 2010/2011, 2013/2014, 2016/2017
This year in the cycle concentrates on readings from the Gospel of Mark. During common year, Year B also deals with the early part of Genesis, 1 Samuel, 2 Samuel, Job, 2 Corinthians, Ephesians, James, and Hebrews.
Year B is used for: 2005/2006, 2008/2009, 2011/2012, 2014/2015, 2017/2018
Year C is used for: 2006/2007, 2009/2010, 2012/2013, 2015/2016, 2018/2019