II. Baptism is to be administered at Easter-tide and not on the Epiphany.
Accordingly when it reached my ears on reliable testimony (and I already felt a brother's affectionate anxiety about your acts, beloved) that in what is one of the chief sacraments of the Church you depart from the practice of the Apostles' constitution by administering the sacrament of baptism to greater numbers on the feast of the Epiphany than at Easter-tide, I was surprised that you or your predecessors could have introduced so unreasonable an innovation as to confound the mysteries of the two festivals and believe there was no difference between the day on which Christ was worshipped by the wise men and that on which He rose again from the dead.
You could never have fallen into this fault, if you had taken the whole of your observances from the source whence you derive your consecration to the episcopate; and if the see of the blessed Apostle Peter, which is the mother of your priestly dignity, were the recognized teacher of church-method. We could indeed have endured your departure from its rules with less equanimity, if you had received any previous rebuke by way of warning from us. But now as we do not despair of correcting you, we must show gentleness. And although an excuse which affects ignorance is scarce tolerable in priests, yet we prefer to moderate our needful rebuke and to instruct you plainly in the true method of the Church.
Source: Letters (New Advent)