1) The winter volume (pars hiemalis) comprising the Offices of Advent, Christmastide, and Epiphany, up to and including the Saturday before the First Sun. day of Lent. In the calendar of the fixed feasts, this part extends from November 26 to March 12.
2) The spring volume (pars verna) containing the Offices of Lent and Paschaltide to the Saturday of the Pentecost Ember Week, inclusive. In the fixed calendar, this period begins with February 7 and lasts to June 19.
3) The summer volume (pars aestiva) with the time after Pentecost up to the Fifteenth Sunday, inclusive. For the fixed feasts, this section runs from May 18 to September 2.
4) The autumn volume (pars autumnalis) covering the year from the Eleventh Sunday after Pentecost till the day before Advent, August 28 to December 2 of the fixed calendar."