(표준 객체) Date 객체
let date = new Date();
date = new Date('December 9, 1991');
date = new Date('December 9, 1991 02:24:23');
date = new Date(1991, 12, 9, 2, 24, 23, 1);
let date = new Date();
date = new Date('December 9, 1991');
date = new Date('December 9, 1991 02:24:23');
date = new Date(1991, 12, 9, 2, 24, 23, 1);