If - like me - you became a Christian from a non-churchgoing background in the late 1980s or early 1990s and attended a Church of England church, then your first liturgical encounter would be with the Alternative Service Book. It would be confusing to hear older people reminisce about Series 1, Series 2, Series 3 and Series 2 & 3 Combined.
A key part of any service book is its calendar. The Church calendar plays a role in helping us remember parts of Jesus's life, death and resurrection, and the actions of God in His story of redemption - not just the familiar Easter and Christmas Day, but the Epiphany (6 January), Transfiguration (6 August), Ascension Day etc.
One of the ways that I feel Common Worship has improved on the Book of Common Prayer is its handling of November. In the BCP, you had Advent Sunday, which would be between 27 November and 3 December inclusive, with the Last Sunday after Trinity being the Sunday before that (i.e. between 20 and 26 November inclusive).
November is a heavy month. The nights draw in, frosts appear, deciduous trees are bare, flowers die. There is this element of death and decay - and that month sees All Saints' Day (1 November) and All Souls' Day (2 November), as well as Remembrance Sunday (which, for obvious reasons, the Reformers would not have known about).
Common Worship draws this together into its own little liturgical season, starting with All Saints' Sunday, 4 weeks before Advent - hence between 30 October and 5 November inclusive. This means that its Last Sunday after Trinity is 4 weeks before the one in the BCP (so will be between 23 and 29 October inclusive). Before we get into the rush of Christmas and our celebrating of the birth of Jesus, we reflect on our own mortality.
Under the ASB calendar, Common Worship's Last Sunday after Trinity would be 9 Before Christmas, as the Church of England bought into the secular idea that Christmas needed a nice long period of preparation.
And so the Sunday between 16 and 22 October inclusive (i.e. last Sunday) would be on the calendar as the Last Sunday after....
No, not Trinity.
Trinity Sunday can be as early as 17 May or as late as 20 June. There is that long period in the church calendar where Sundays are named after how many weeks they are after it.
The Alternative Service Book used a different starting point - the Sunday before Trinity, which is Whit Sunday (in the BCP) and Pentecost (in Common Worship). This celebrates the day that the Holy Spirit came upon the Apostles and the others in the upper room, empowering them to bring the Christian Gospel across the known world.
The nth Sunday after Pentecost is the (n-1)th Sunday after Trinity.
This seems, to me, to be the better starting point. The Church's mission, and our individual lives, rely on the empowering of the Holy Spirit. Naming our Sundays after Pentecost puts the focus, correctly, on this.