THE GRADUAL AND PENITENTIAL PSALMS
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.