Checking Whether a Year Is a Leap Year

In this lesson you will learn how to test whether a year is a leap year in Kotlin, covering how to combine several conditions into one decision. This is for anyone searching for "Kotlin leap year check implementation".

A year is a leap year if it is divisible by 4 but not by 100, or if it is divisible by 400. It is basic logic that appears in calendar and date-calculation programs.

The sample code expresses this whole rule in the single expression (year % 4 == 0 && year % 100 != 0) || year % 400 == 0. 2024 is divisible by 4 and not by 100, so it is a leap year; 1900 is divisible by 100 but not by 400, so it is not.

A common stumbling block for beginners is testing only for multiples of 4. The famous examples are 2000, which is divisible by 400 and so is a leap year, and 1900, which is divisible by 100 but not 400 and so is not.

In real-world development this leap-year logic is essential for accurate day counts whenever you implement date arithmetic or calendar features.

📖 Reference code

fun isLeapYear(year: Int): Boolean {
    return (year % 4 == 0 && year % 100 != 0) || year % 400 == 0
}

fun main() {
    println(isLeapYear(2024))
    println(isLeapYear(2023))
    println(isLeapYear(1900))
}

✍️ Your code

Type your code, then press "Run"

🧪 This site can't compile or run Kotlin directly, so it checks on the spot whether what you typed matches the reference code (scoring happens entirely in your browser — nothing is sent anywhere).