A tradition recorded in the Liber Pontificalis attributes to Pope Telesphorus (128–139?) the use of the hymn at the Mass of Christmas Day and to Pope Symmachus (498–514) its use on Sundays and the feasts of martyrs, but only by bishops; the right to use it was later extended to priests, at first only at Easter and on the day of their ordination, but by the end of the 11th century priests, as well as bishops, used it in the Mass on Sundays and feasts outside of Lent and Pre-Lent. After the 12th century Advent began to be considered a penitential period in imitation of Lent, to the exclusion therefore of the "Gloria in excelsis Deo".