From Advent until Pentecost, the Church meditates upon the life and work of Christ. In the season of Trinity (or the Sundays after Pentecost, as some churches call it), we reflect how the work of God expresses itself in the Christian life. This long season, which runs from about June until December, is actually divided into four parts. Doing this helps us see the themes of the longer season and digest the lessons we hear from Sunday to Sunday.
Trinity I
This section is made up of six Sundays. On the first Sunday we pause to consider how God has revealed Himself to us in the Holy Trinity. The five Sundays after this tell us something of God’s Church. In many ways these Sundays are a continuation of the celebration of Pentecost, for during this time we will hear how the Holy Spirit “calls, gathers, enlightens and sanctifies the whole Christian Church on earth, and keeps it with Jesus Christ in the one true faith. -Laache: Book of Family Prayer p. 383.
Trinity II (St. John’s Tide)
The 6th through 18th Sundays after Trinity all tell of the growth and fruit of the Christian life. During this time of the Church Year we hear many of the parables of Jesus, and are encouraged in our daily cycle of repentance and renewal. This period is sometimes called “St. John’s Tide,” since it usually follows soon after the festival of St. John the Baptist (June 24). The words of St. John, “He must increase; I must decrease” nicely sum up the theme of this time of the Church Year. -Laache: Book of Family Prayer p. 458.