Although 2017 is the 500th anniversary of Martin Luther nailing his 95 theses to the Wittenberg door, there’s another religious anniversary -– a centennial -– this past Friday that got far less publicity.

Oct. 13, 1917, is the date when some 70,000 people, including a few newspaper reporters, witnessed the “miracle of the sun” in Fatima, a town north of Lisbon in central Portugal.

Many dismiss this as outdated Catholic lore, but the alleged appearance of the Virgin Mary in Fatima was a big deal for St. Pope John Paul II, who was nearly assassinated on May 13, 1981. He attributed his escape from death to Our Lady of Fatima.

Yet, I found very little about this anniversary in the secular media. The Philadelphia Inquirer was one of the exceptions, possibly because the local archbishop, Charles Chaput, made its observance a priority.

Throughout the year, the Archdiocese of Philadelphia’s 1.5 million Catholics have been observing the anniversary with special services, lectures, movie screenings, retreats, and pilgrimages.  Archbishop Charles J. Chaput will preside over a consecration service at 11 a.m. Sunday at the Cathedral Basilica of SS. Peter and Paul.

Fatima is among the three most popular Marian apparitions, including one reported in 1858 by St. Bernadette Soubirous in Lourdes, France (Our Lady of Lourdes), and another in 1531 by St. Juan Diego and his uncle on the Hill of Tepeyac near Mexico City (Our Lady of Guadalupe), according to Jason Paul Bourgeois, an assistant professor at the International Marian Research Institute at the University of  Dayton in Ohio.

Messages of prayer, penance, reparations for sin, and devotion to Mary are oft-repeated in Marian sightings, but Our Lady of Fatima’s three secrets — prophecies and apocalyptic visions of specific events to come — set it apart.

The story is quite complete, going into the history of the three secrets of Fatima as well as other Marian apparitions. My only complaint is that it gave too much credence to those debunking the “miracle of the sun” -- in that how does one deceive 70,000 people? The skeptics never explain that one.