const event = new Date('August 19, 1975 23:15:30');
event.setHours(20);

console.log(event);
// Expected output: "Tue Aug 19 1975 20:15:30 GMT+0200 (CEST)"
// Note: your timezone may vary

event.setHours(20, 21, 22);

console.log(event);
// Expected output: "Tue Aug 19 1975 20:21:22 GMT+0200 (CEST)"