The Wednesdays, Fridays and Saturdays of these weeks are the Ember days distinctively, the following Sundays being the days of ordination.
Advent; the days between Septuagesima and Maundy Thursday; vigils that fall on fast days, and Ember days, except the vigil before Whitsunday (red) and the Ember days in Whitsun week (red).
It is worn, too, on the vigils of fasts, Ember Days and days of intercession, on the Feast of Holy Innocents (if on a week-day), at litanies, penitential processions, and at other than solemn benedictions and consecrations.
The observance of the Ember days is confined to the Western Church, and had its origin as an ecclesiastical ordinance in Rome.
From Rome the Ember days gradually spread through the whole of Western Christendom.