St. Pius V., in his Bull Quod a nobis, July 9, 1568, granted -
i. An indulgence of fifty days, to all the faithful, every time that under
obligation they say devoutly the Gradual or Penitential Psalms on the days
prescribed by the rubrics of the Renian Breviary.
ii. Forty days indulgence to those who say them at any other time for their
own devotion. See his Bull Superni omnipotentis Dei, April 5, 1571.