count-leap-years.js

function countLeapYears(date) {
    let years = 0;
    for (let year = 1; year < date.getFullYear(); year++) {
        if (year % 4 === 0 && (year % 100 !== 0 || year % 400 === 0)) {
            years++;
        }
    }
    return years;
}