private string Dtime() 
{ 
 byte tempB = (byte)DateTime.Now.DayOfWeek; 
 byte dayByte = (byte)DayOfWeek.Wednesday; 
 DateTime wednesdayNow = DateTime.Now.AddDays(dayByte - tempB);
 //本星期三 
 DateTime returnTime = new DateTime (); 
 if (DateTime.Now.DayOfWeek < wednesdayNow.DayOfWeek) 
 { 
  //当前星期小于本星期三 获取本周星期三 
  returnTime = new DateTime(wednesdayNow.Year,wednesdayNow.Month,wednesdayNow.Day,10,0,0);
 } 
 else 
 { 
  //当前星期大于本星期三 获取下周星期三 
  DateTime nextWednesday = wednesdayNow.AddDays(7);//下周三 
  returnTime = new DateTime(nextWednesday.Year,nextWednesday.Month,nextWednesday.Day,10,0,0);
 } 
 return returnTime.ToString() 
}

$(document).ready(function() {
 $('body').everyTime('1s', function() {
 var nowDate = new Date();
 var endDate = new Date($("#sp_next").html().replace(//-/g, "//"));
 //这个时间是上个方法返回的时间
 var timeold = endDate.getTime() - nowDate.getTime();
 var sectimeold = timeold / 1000
 var secondsold = Math.floor(sectimeold);
 var msPerDay = 24 * 60 * 60 * 1000
 var e_daysold = timeold / msPerDay
 var daysold = Math.floor(e_daysold);
 var e_hrsold = (e_daysold - daysold) * 24 + (daysold * 24);
 var hrsold = Math.floor(e_hrsold);
 var e_minsold = (e_hrsold - hrsold) * 60;
 var minsold = Math.floor((e_hrsold - hrsold) * 60);
 var seconds = Math.floor((e_minsold - minsold) * 60);
 if (hrsold > 0 && hrsold < 10) { hrsold = "0" + hrsold; }
 if (minsold < 10) { minsold = "0" + minsold; }
 if (seconds < 10) { seconds = "0" + seconds; }
 if (hrsold < 0) {
  $(".seckill_time").html("0");
  $(".seckill_minute").html("0");
  $(".seckill_second").html("0");
 } else {
  $(".seckill_time").html("").html(hrsold);
  $(".seckill_minute").html("").html(minsold);
  $(".seckill_second").html("").html(seconds);
 }
 });
});