cassidoo_feb_02_2026.js

// thanks: https://stackoverflow.com/a/16353241
const isLeapYear = year => 
    (
        // divisible by 4 but not 100
        (year % 4 == 0) && (year % 100 != 0)
    ) || (
        // divisible by 400
        year % 400 == 0
    );

const isPerfectMonth = year =>
    // must be a year where Feb has 28 days
    !isLeapYear(year)
    &&
    // starts on either a Sunday or a Monday
    new Date(year, 1, 1).getDay() < 2; 

const nextPerfectMonth = year =>
    isPerfectMonth(year) ? year : nextPerfectMonth(year + 1);

const previousPerfectMonth = year =>
    isPerfectMonth(year) ? year : previousPerfectMonth(year - 1);

const nearestPerfectMonths = year =>
    ({ 
        prev: `${previousPerfectMonth(year)}-02`,
        next: `${nextPerfectMonth(year + 1)}-02`
    });