建構函式
Date 物件的建構函式有以下4種:
(1)var variable = new Date();
(2)var variable = new Date(millisenconds);
(3)var varibale = new Date('yyyy/MM/dd hh:mm:ss');
(4)var variable = new Date(year, month, day, hours, minutes, seconds, milliseconds);
X月份有多少天
new Date(year, X, 0).getDate(); //(月份從0算起,(X+1)月份的第0天,即X月份的最後一天)