var cenaNochevieja = new Date(2014, 11, 31, 22, 30, 0);

var anyo = cenaNochevieja.getFullYear();

var mes = cenaNochevieja.getMonth();

var diaMes  = cenaNochevieja.getDate();

var incognita = new Date(cenaNochevieja.setDate(diaMes + 1));

​

console.log(incognita);

​

var cenaPreNochevieja = new Date(2014, 11, 30, 22, 30, 0);

var cenaNochevieja = new Date(2014, 11, 31, 22, 30, 0);

var cenaNochevieja2 = new Date(2014, 11, 31, 22, 30, 0);

​

console.log( cenaPreNochevieja < cenaNochevieja ); // true

console.log( cenaNochevieja == cenaNochevieja2 ); // false

console.log( cenaNochevieja === cenaNochevieja2 ); // false

console.log( cenaNochevieja.getTime() == cenaNochevieja2.getTime() ); // true

console.log( cenaNochevieja.getTime() === cenaNochevieja2.getTime() ); // true

​