Every day in the Church is some saint’s day. There are so many of them, that not a day goes by or we don’t commemorate a handful, and that’s not even counting all those who we don’t know, but who lived no less holy lives. These feast days of saints are neatly structured according to the Martyrologium Romanum: each saint his own day (unless you’re the Blessed Virgin Mary, for example; she gets a bunch of feast days throughout the year).
Leap years are a bit problematic. According to the general logic of the martyrology, the saints whose feast falls on 29 February are commemorated only once every four years. And that won’t do, of course. A cursory search of the Internet reveals at least four saints whose feast day falls today, but they are all transferred from either yesterday or tomorrow. The Church seems to abhor a vacuum of saints on any given day, it would seem. Moved back from yesterday are, for example, St. Hilarius, pope from 461 to 468, and Saints Romanus and Lupicinus, two fifth-century hermit brothers in eastern France. Moved forward from tomorrow are, for example, Saint Albinus of Angers, sixth-century monk and bishop from Britanny, and St. Oswald of Worcester, tenth-century archbishop of York.
The Church may have been the instigator of our modern calendar with its leap years, but even she has to be creative when it comes to the feast days of saints.