Is it a leap year?
Whether any year is a leap year, and why.
Any year from 1583 to 4000. The Gregorian calendar begins in 1582.
The part that catches people out
Divisible by four is only the first of three rules. A century year is not a leap year unless it also divides by 400 — so 2000 was one and 1900 was not, and 2100 will not be.