The second Vatican Council, in its constitution on the Liturgy, initiated a reform of the Divine Office to adapt it to the needs of modern times. The amount of Office that those bound to the Breviary were obliged to recite was to be reduced, and it was stressed that the Office is intended to sanctify the whole day, so that each Hour should be recited at the time appropriate to it, Lauds and Vespers being seen as the most important Hours. The Council also emphasised that the Office is the common prayer of the whole Church, and urged secular clergy and laypeople as well as religious to come together to recite it in common.

The publication in 1970 of the Liturgia Horarum, the Latin version of the revised Divine Office, was a major step towards the fulfillment of the Council’s intentions. It should not be seen as the end of the process, for liturgy as envisaged by the Council is a creative activity, demanding continual adaptation for the needs of particular groups and situations. For this reason, the Liturgia Horarum gives great scope for choice and adaptation : it is nearly always permissible to change the psalms, antiphons or readings to suit the individual or group that is celebrating the Liturgy of the Hours. This is emphasised in the fine ‘General Instruction’ with which the Liturgia Horarum is prefaced, a document that should be read by all for whom the Liturgy of the Hours forms a part of prayer. The published texts are a framework within which much variation is desirable and possible, and so a habit of reciting the Office that paid too much attention to discovering and observing precisely ‘what is laid down in the book’ would be alien to the spirit of the Council and its reformed liturgy.