你可以用这种方法减去小时数

var valuestart = $("select[name='timestart']").val();
var valuestop = $("select[name='timestop']").val();

//create date format          
var timeStart = new Date("01/01/2007 " + valuestart).getHours();
var timeEnd = new Date("01/01/2007 " + valuestop).getHours();

var hourDiff = timeEnd - timeStart;

这是一把工作中的小提琴http://jsfiddle.net/VnwF7/4/
UPDATE -计算是否包含第二天。只需添加以下if块

if (hourDiff < 0) {
    hourDiff = 24 + hourDiff;
 }

http://jsfiddle.net/gfvhqat9/

试试这个方法

var time_start = new Date();
var time_end = new Date();
var value_start = "06:00:00".split(':');
var value_end = "23:00:00".split(':');

time_start.setHours(value_start[0], value_start[1], value_start[2], 0)
time_end.setHours(value_end[0], value_end[1], value_end[2], 0)

time_end - time_start // millisecond

我修改了您的代码，以便只使用差异，而不必创建另一个date对象：

$(document).ready(function() {    
function calculateTime() {
        //get values
        var valuestart = $("select[name='timestart']").val();
        var valuestop = $("select[name='timestop']").val();

         //create date format          
         var timeStart = new Date("01/01/2007 " + valuestart);
         var timeEnd = new Date("01/01/2007 " + valuestop);

         var difference = timeEnd - timeStart;             

         difference = difference / 60 / 60 / 1000;

    $("p").html("<b>Hour Difference:</b> " + difference)             

}
$("select").change(calculateTime);
calculateTime();
});​

它不是Jquery，而是JavaScript中与时间和日期相关的所有内容...
这可能有助于：日期http://code.google.com/p/datejs/
下面是一些日期和时间计算从文档

Date.today().set({ day: 15 })          // Sets the day to the 15th of the current month and year. Other object values include year|month|day|hour|minute|second.

        Date.today().set({ year: 2007, month: 1, day: 20 })

Date.today().add({ days: 2 })          // Adds 2 days to the Date. Other object values include year|month|day|hour|minute|second.

        Date.today().add({ years: -1, months: 6, hours: 3 })

Date.today().addYears(1)               // Add 1 year.
Date.today().addMonths(-2)             // Subtract 2 months.
Date.today().addWeeks(1)               // Add 1 week
Date.today().addHours(6)               // Add 6 hours.
Date.today().addMinutes(-30)           // Subtract 30 minutes
Date.today().addSeconds(15)            // Add 15 seconds.
Date.today().addMilliseconds(200)      // Add 200 milliseconds.

Date.today().moveToFirstDayOfMonth()   // Returns the first day of the current month.
Date.today().moveToLastDayOfMonth()    // Returns the last day of the current month.

new Date().clearTime()                 // Sets the time to 00:00 (start of the day).
Date.today().setTimeToNow()            // Resets the time to the current time (now). The functional opposite of .clearTime()

编辑：由于这是一个相当老的答案，我最近也使用moment.js进行与日期相关的操作，这也非常有用。

你不需要把它们转换成这个特定情况下的日期。

$(document).ready(function() {    
    function calculateTime() { 
        var hourDiff = 
        parseInt($("select[name='timestart']").val().split(':')[0],10) -         
        parseInt($("select[name='timestop']").val().split(':')[0],10);

        $("p").html("<b>Hour Difference:</b> " + hourDiff )         
    }
    $("select").change(calculateTime);
    calculateTime();
});

Working fiddle

• 这段代码对我很有效，代码是考虑到AM PM的差异而编写的。只要根据你喜欢的格式写日期，试试这段代码 *

function getTimeDifference(startTime, endTime) {
  const difference = endTime - startTime;
  const differenceInMinutes = difference / 1000 / 60;
  let hours = Math.floor(differenceInMinutes / 60);
  if (hours < 0) {
    hours = 24 + hours;
  }
  let minutes = Math.floor(differenceInMinutes % 60);
  if (minutes < 0) {
    minutes = 60 + minutes;
  }
  const hoursAndMinutes = hours + ":" + (minutes < 10 ? '0' : '') + minutes;
  return hoursAndMinutes;
}

const start = new Date(0,0,0,23,15);
const end = new Date(0,0,0,1,30);
const difference = getTimeDifference(start, end);
console.log(difference);