function getNumberOfDays($year:int, $month:int):int { var month:Date = new Date($year, $month + 1, 0); return month.date; } //jan trace(getNumberOfDays(2010, 0)); // traces 31 //feb trace(getNumberOfDays(2010, 1)); // traces 28 //dec trace(getNumberOfDays(2010, 11)); // traces 31
[ActionScript 3.0] AS3 获取某年某月的天数(Get number of days in a month)
原文：http://www.cnblogs.com/frost-yen/p/5200663.html