Broadly speaking, the Church Year is divided into several “Times,” demarcated in relation to the great Feasts of Christmas and Epiphany, Easter and Pentecost. These Times, in turn, are further subdivided into significant “seasons” or more subtle “tides,” generally hinged upon some of the other festivals of the Church Year. The Time of Christmas moves from Advent through Christmas into Epiphany; the Time of Easter extends from Lent through Holy Week into Eastertide, culminating in the Day of Pentecost; and the Time of the Church follows after Eastertide and continues until Advent.
The contours of the Time of the Church follow some of the key festivals occurring along the way, beginning with the Feast of the Holy Trinity, emphasizing the Father, Son, and Holy Spirit as the Fountain and Source of all things (Trinity Tide). “Apostles’ Tide” highlights the ministry of God’s servants, the Apostles and Prophets (from the Feast of St. Peter & St. Paul on 29 June). “Martyrs’ Tide” recalls the witness of His holy martyrs under the sign of the Holy Cross (from the Commemoration of St. Lawrence on 10 August). And “Angels’ Tide” revels in the service of His holy angels on behalf of the Church Militant (from the Feast of St. Michael & All Angels on 29 September). Finally, “All Saints’ Tide” focuses on the eschatological hope and promise of all Christians in the coming of the Lord Jesus Christ (from the Feast of All Saints on 1 November).
Over the years, various scholars have identified subtle themes in the lections appointed for the Sundays in the historic one-year lectionary in the Time of the Church. The first four Sundays after Holy Trinity, for example, accentuate and emphasize the work of the Holy Spirit in the life of the Church, furthering the focus of Pentecost Day (Trinity Tide). The Holy Gospels for the Fifth through Eighteenth Sundays after Trinity address the growth and fruits of Christian faith and love, nurtured by the Apostolic Ministry of the Gospel (Apostles’ Tide), and manifested in the bearing of the Cross, even unto death (Martyrs’ Tide). The Nineteenth through Twenty-Fifth Sundays after Trinity, typically following the Feast of St. Michael & All Angels, highlight the spiritual warfare of the Church against the devil, the world, and all the principalities and powers of this present evil age (Eph. 1:21; 6:12). And the final Sundays of the Church Year focus on the hope and promise of the Resurrection in view of the glorious coming of Christ Jesus for the final judgment (Pre-Advent or All Saints’ Tide). Due to the shifting date of Easter, this progression of the Sundays often does not line up in close proximity with the corresponding festivals and tides. The patterns, however, remain and may be followed in a way that is still helpful.
This grouping of Sundays on the basis of the same key festivals is also quite feasible and fits nicely in the three-year lectionary. For example, the “First Sunday in Apostles’ Tide” would correspond to “Proper 8” (the Sunday occurring within a few days before or after the Feast of St. Peter & St. Paul). Similarly, “the First Sunday in Martyrs’ Tide” would always correspond to “Proper 14,” and “the First Sunday in Angels’ Tide” would always correspond to “Proper 21.”
The point is not to impose an arbitrary thematic upon the Time of the Church. The tides simply offer some gentle contours to this long stretch of weeks and months, which felicitously coincide with the basic trajectories of our Lord’s saving work. What originates in the Holy Trinity and is accomplished in the Cross and Resurrection of the incarnate Son is extended to the nations and established in the Church through the Apostolic Ministry of the Gospel. The preaching of Christ brings the Cross and suffering upon His Church and those who are called to discipleship, but the outcome of this spiritual warfare is secure for those who belong to His Body and Bride, the Church, who die and rise with Him through Holy Baptism in His Name. The Holy Gospels likewise follow this same general trajectory: As the Son comes down from the Father in heaven, He calls and sends His Apostles in His Name, even as He calls disciples to take up the Cross and follow Him to death; and in His Resurrection from the dead, He sends His men and angels to guard and protect His Church on earth through the preaching of His Word and the giving of His Body and Blood to His disciples. So do His people lift up their heads in the hope and promise of His coming, knowing that His Redemption is drawing near in the midst of the great tribulation.
(For more information on the Church Year and Lectionary, see my essay in the LSB: Companion to the Services, CPH, 2022, from which the above paragraphs are extracted and redacted.)