The leap day, February 29, occurs once every 4 years, or more accurately, 97 times every 400 years, according to the Gregorian Calendar. The latter is named after Pope Gregory XIII who improved the calendar in 1582 when the spring equinox had shifted far from March 21 in the Julian Calendar.
There is not much special about this leap day in the Catholic Church, except that those few saints commemorated on this day in the Roman Martyrology are probably greatly rejoicing in heaven. As a general rule provided in GIRM (§355), priests can choose to celebrate the memorial of any saint of the day commemorated in this authoritative liturgical book Roman Martyrology, even if the saint is not in the General Roman Calendar or local calendar, unless other memorials or feasts impede it.
There is one interesting fact that no one else seems to know about the leap day. Statistically, the leap day is the day in the whole year when bishops were most likely to die from the year 1940 to 2015.
Rather than using 1940 as a starting date, let us start from the year 1900, with the data from the GCatholic.org, to explore the interesting statistical analysis of the date of the death of bishops.
There are a total of 9,698 Catholic bishops whose date of death is known in the years 1900 to 2015. On average, 83.6 bishops died every year during this period. There are 43 bishops who died on August 2 (feast of the Portiuncula) in these 116 years (hence 0.37 deaths/year), while 10 bishops died on February 29 in the 28 leap years (hence 0.36 deaths/year) in this period of time. On the other end, October 29 is the lucky day on which the fewest number (11) of bishops died.
In this second graph, you can see the monthly rate of death of bishops since 1900. December to March and August have the highest rate. This is probably due to the winter months and August heat in the northern hemisphere where the majority of bishops reside. June and September are the safest months for bishops.
Let us celebrate this leap day with great devotion to the Lord, and pray for our bishops, with a leap of faith!