const isLongYear = (year) => { const jan1 = new Date(year, 0, 1); const dec31 = new Date(year, 11, 31); return (4 == jan1.getDay() || 4 == dec31.getDay()) } for (let y = 1995; y <= 2045; y++) { if (isLongYear(y)) { console.log(y) } }