JavaScript特定月份的天数

Question

有人能指出我正确的方向吗？我试图找出特定范围内有多少天。如果我有预订日期范围，例如'2013年1月18日21:00'和'2013年2月4日15:00'，并想知道2月1日到4月30日之间有多少天。经过大量的摆弄，我可能会有它......？

    /* The test date range */
    var startTime = "18 Jan 2013 21:00";
    var endTime = "4 Feb 2013 15:00";

    /* Set up the range to test against*/
    var rangeStart = Date.parse ("1 Feb 2013 00:00");
    var rangeEnd = Date.parse ("30 Apr 2013 00:00");

    var start = Date.parse(startTime); 
    var end = Date.parse(endTime);

    var numOfHrs =  Math.ceil((end-start) / (1000*60*60));
    var numOfDays = Math.ceil(numOfHrs/24);
    var rangeCrossed = 0;   


    if (end > rangeStart){ /* A valid crossover period may exist */

        /* Start time before or equal range start and end less than or equal the range end */
        if ((start<=rangeStart) && (end <= rangeEnd)) { rangeCrossed = end-rangeStart } 
        /*Start greater than or equal to the range start and less than the range end */
        else if ((start>=rangeStart) && (start<rangeEnd)) 
                {
                /* start and end both within range */
                if (end<=rangeEnd) { rangeCrossed = end-start } 
                /* start after range start and end after range end */
                else {rangeCrossed = (rangeEnd-start) + (end-rangeEnd)}; 
                } 
        /*full range crossed */     
        else if (start<=rangeStart && end >=rangeEnd) { rangeCrossed = rangeEnd-rangeStart};    
        }

    alert((rangeCrossed/(1000*60*60)/24))