The most compelling reason to celebrate the 100th anniversary of the apparitions of Fatima is that they have a unique character that other Marian apparitions do not have... God marked these apparitions with exceptional signs.
In the first place, these apparitions have been authenticated by a rarely seen cosmic miracle. By cosmic miracle we mean a miracle acting on elements observable over tens of kilometers away, and by several thousand people at once.
Before the apparitions of Fatima, there have only been three events with these characteristics: the Great Flood, the sunrise during the battle of Joshua against the Amorites (Joshua 10: 12-13) and the darkened skies of Good Friday. The miracle of the sun is the fourth event of this nature in human history.
We may add that the apparitions of Fatima were authenticated by another cosmic miracle: the “catching on fire” of the sky on the night of January 25-26, 1938, an event admittedly subsequent to the apparitions but predicted by Our Lady in the secret given on July 13, 1917.