In addition to today being First Friday and the feast of Saint Alphonsus Ligouri with a commemoration of Saint Stephen I, it is 2 August, the date of the annual Portiuncula indulgence.
This indulgence began, according to the Franciscans, in the 13th century, likely making it the oldest plenary indulgence in the Church. The Portiuncula chapel had been neglected by the Benedictines, but eventually given to Saint Francis of Assisi with the intention of him creating a new religious order (and restoring the chapel). In 1209, the Order of Friars Minor was founded. The order would sadly split numerous times, with turbulence and rupture still occurring between Franciscans today. But the chapel has been under the care of Franciscans ever since their founding, and has hosted general chapters and a visit from Saint Clare of Assisi. Saint Francis died just feet from the chapel.
The Catholic Encyclopedia gives this history on the indulgence:
The Portiuncula Indulgence could at first be gained only in the Portiuncula chapel between the afternoon of 1 Aug. and sunset on 2 Aug. On 5 Aug., 1480 (or 1481), Sixtus IV extended it to all churches of the first and second orders of St. Francis for Franciscans; on 4 July, 1622, this privilege was further extended by Gregory XV to all the faithful, who, after confession and the reception of Holy Communion, visited such churches on the appointed day. On 12 Oct., 1622, Gregory granted the same privilege to all the churches of the Capuchins; Urban VIII granted it for all churches of the regular Third Order on 13 Jan., 1643, and Clement X for all churches of the Conventuals on 3 Oct., 1670. Later popes extended the privilege to all churches pertaining in any way to the Franciscan Order, even to churches in which the Third Order held its meetings (even parish churches, etc.), provided that there was no Franciscan church in the district, and that such a church was distant over an Italian mile (1000 paces, about 1640 yards). Some districts and countries have been granted special privileges. On 9 July, 1910, Pius X (only, however, for that year) granted the privilege that bishops could appoint any public churches whatsoever for the gaining of the Portiuncula Indulgence, whether on 2 Aug. or the Sunday following (Acta Apostolicae Sedis, II, 1910, 443 sq.; Acta Ord. Frat. Min., XXIX, 1910, 226). This privilege has been renewed for an indefinite time by a decree of the S. Cong. of Indul., 26 March, 1911 (Acta Apostolicae Sedis, III, 1911, 233-4). The Indulgence is toties-quoties, that is, it may be gained as often as one wishes (i.e. visits the church); it is also applicable to the souls in purgatory.
Following Vatican II, it survived the reforms of Paul VI:
In addition, a plenary indulgence can be acquired twice a year in parish churches: on the feast of the church's titular saint and on August 2, when the "Portiuncula" occurs, or on some other more opportune day determined by the Ordinary.
To receive the plenary indulgence, recite the Credo and Pater Noster -- under the usual conditions for obtaining a plenary indulgence, including confession, communion and prayers for the intentions of the Holy Father -- in any parish church, cathedral or minor basilica today. For those curious about Pope Francis' intentions, for the month of August his general intention is "That parents and teachers may help the new generation to grow in upright conscience and life" and the mission intention is "That the local Church in Africa, faithfully proclaiming the Gospel, may promote peace and justice."
The Portiuncula chapel is now located in the Basilica of Saint Mary of the Angels.