51 We think the following seasons would be particularly opportune: Advent, when we recall the expectation of a Savior by the human race as well as the providential preparations for the coming of the Savior; the feast of Epiphany which reveals the Savior born among men; and Pentecost when we celebrate the foundation of the Church under the inspiration of the Holy Ghost.
Source: Fidei Donum (Vatican.va)