This is taken from the present Liturgy of the Hours:
APOSTOLIC CONSTITUTION PROMULGATION
THE DIVINE OFFICE
REVISED BY DECREE OF THE
SECOND VATICAN ECUMENICAL COUNCIL
PAUL, BISHOP
Servant of the Servants of God
For an Everlasting Memorial
“…We decree that this new Liturgy of the Hours may be brought into use as soon as it is published. Meanwhile, the episcopal conferences should see to the preparation of editions of this liturgical work in the vernacular and, after approval and confirmation by the Apostolic See, should fix the date when vernacular versions may or must be used, either in whole or in part. Beginning on the day when these vernacular versions are to be used for vernacular celebrations, only the revised form of the Liturgy of the Hours is to be followed by those who continue to use Latin.
It is lawful, however, for those who because of advanced age or for special reasons experience serious difficulties in observing the new rite, to continue to use the former Roman Breviary, in whole or in part, with the consent of the Ordinary, and exclusively in individual recitation.
We wish that these decrees and prescriptions be firm and effective now and in the future, notwithstanding, to the extent necessary, Apostolic Constitutions and Ordinances issued by our predecessors, and other prescriptions, even those deserving particular mention and derogation.
Given at Rome, at Saint Peter’s, on the feast of All Saints, November 1, 1970, the eighth year of our pontificate.
PAUL VI, POPE