Many of you will live to the year 2100, which is not a leap year. Not all years which are divisible by 4 are leap years. A centennial year (multiple of 100) is a leap year only if it is not divisible by 400. So 2000 is (was) a leap year, 2400 is a leap year, but 2100 and 2200 are not leap years. Non-centennial years which are multiples of 4 are always leap years. If P is the statement
and Q is the statement and R is the statement
P: ”L mod 4 = 0”
Q: ”L mod 100 = 0” R: ”L mod 400 = 0”
For example, the years 1600, 2000, and 2400 are century leap years since those numbers are divisible by 400, while 1700, 1800, 1900, 2100, 2200, and 2300 are common years despite being divisible by 4.
