6 This is the reason why - trusting much to your zeal and episcopal authority, Venerable Brethren, and not doubting that the good and pious faithful will run beyond the mere letter of the law - We prescribe that during the whole month of October, at the recitation of the Rosary, for which We have already legislated, a prayer to St. Joseph be added, the formula of which will be sent with this letter, and that this custom should be repeated every year. To those who recite this prayer, We grant for each time an indulgence of seven years and seven Lents. It is a salutary practice and very praiseworthy, already established in some countries, to consecrate the month of March to the honour of the holy Patriarch by daily exercises of piety. Where this custom cannot be easily established, it is as least desirable, that before the feast-day, in the principal church of each parish, a triduo of prayer be celebrated. In those lands where the 19th of March - the Feast of St. Joseph - is not a Festival of Obligation, We exhort the faithful to sanctify it as far as possible by private pious practices, in honour of their heavenly patron, as though it were a day of Obligation.
Source: Quamquam Pluries (Vatican.va)