2. A grave occupation excuses from the whole or from a part of the
Office. Thus, missioners giving missions or parish retreats are excused
from the whole Office; so, too, are priest combatants in the battle
line; but when in rest camps they are bound to say the Hours. A priest
engaged in saying his Office, if he receive an urgent call to a dying
person may not have time to finish his Office before midnight. He is
exempt from the part of the Office omitted and does not sin by the
omission. The proposition claiming exemption from the Office for those
engaged in great studies was condemned by Pope Alexander VII. The
biographers of Lamennais trace the beginning of his downfall to his
exemption from his daily Office.

A difficulty arises sometimes as regards the full or partial or
non-exemption of those who foresee that serious occupation which cannot
be neglected must arise to prevent the recitation of the Hours. In such
cases priests are bound to recite the Office, or as much of it as
possible, within the limits of the current day. In doing this they may
anticipate the times fixed for the recitation of the small Hours, and
they may anticipate Vespers and Compline by reciting them in the
forenoon. If a priest foresees that he may not be able to recite Matins
for next day he is not bound to anticipate, as there is no obligation to
anticipation; the obligation is "recital between midnight and midnight."
It is becoming to anticipate, if possible, so that the Office may be
full and entire. If before midnight there be a cessation from necessary
professional work (e.g., hearing confessions), a priest is bound to
finish his Office for the day or to say as much of it as time allows.
If, however, there be time merely to take a necessary meal before
midnight (e.g., to prepare for a late Mass on next day, Sunday), and
not time to eat and to recite, the obligation of saying the