‘Member back in 2000 when JP2 issued a plenary indulgence for the Jubilee Year? Man, a bunch of people were acting like this was a once-in-a-lifetime opportunity–as if you couldn’t obtain a plenary indulgence on any day you choose.
That being said, the issuing of plenary indulgences of particular occasions doesn’t happen that often, and so it’s notable when it does.
Folks may want to know, therefore, that B16 has issued a plenary indulgence for this Thursday, October 8, which is the feast of the Immaculate Conception and the 40th anniversary of the closing of Vatican II. Thus, according to the OFFICIAL DECREE, the faithful may obtain a pleanary ingulence
if they participate in a sacred rite in its [the Immaculate Conception’s] honour or at least offer an open witness of Marian devotion before an image of Our Lady of the Immaculate Conception, displayed for public veneration, adding the recitation of the Our Father and the Creed and exclamatory invocations to Mary Immaculate, such as "You are All Fair, Mary, and in you there is no stain of original sin!", or "O Queen, conceived without original sin, pray for us!".
Lastly, all the faithful who are prevented from participation by ill health or by another just cause, may obtain on that same day the same gift of the Plenary Indulgence at home or wherever they may be, as long as, with their minds detached from any sin and with the resolution to fulfil the above-mentioned conditions as soon as possible, they are united with spiritual resolve and desire with the intentions of the Supreme Pontiff in prayer to Mary Immaculate and recite the Our Father and the Creed.
All this, of course, is assuming "the usual conditions" for a plenary indulgence are fulfilled, which raises the question: "What are the usual conditions?"
n. 7—To acquire a plenary indulgence it is necessary to perform the work to which the indulgence is attached and to fulfill three conditions: sacramental confession, Eucharistic Communion and prayer for the intentions of the Supreme Pontiff. It is further required that all attachment to sin, even to venial sin, be absent.
If this disposition is in any way less than complete, or if the prescribed three conditions are not fulfilled, the indulgence will be only partial, except for the provisions contained in n.11 for those who are "impeded."
n. 8—The three conditions may be fulfilled several days before or after the performance of the prescribed work; nevertheless it is fitting that Communion be received and the prayers for the intentions of the Supreme Pontiff be said the same day the work is performed.
n. 9—A single sacramental confession suffices for gaining several plenary indulgences, but Communion must be received and prayers for the Supreme Pontiff’s intentions recited for the gaining of each plenary indulgence.
n. 10—The condition of praying for the Supreme Pontiff’s intentions is fully satisfied by reciting one "Our Father" and one "Hail Mary"; nevertheless the individual faithful are free to recite any other prayer according to their own piety and devotion toward the Supreme Pontiff [SOURCE].



