function cdtime(container, targetdate){
  if (!document.getElementById || !document.getElementById(container)) return
  this.container=document.getElementById(container)
  this.currentTime=new Date()
  this.targetdate=new Date(targetdate)
  this.timesup=false
  this.updateTime()
}

cdtime.prototype.updateTime=function(){
  var thisobj=this
  this.currentTime.setSeconds(this.currentTime.getSeconds()+1)
  setTimeout(function(){thisobj.updateTime()}, 1000) //update time every second
}

cdtime.prototype.displaycountdown=function(baseunit, functionref){
  this.baseunit=baseunit
  this.formatresults=functionref
  this.showresults()
}

cdtime.prototype.showresults=function(){
  var thisobj=this
  var timediff=(this.targetdate-this.currentTime)/1000 //difference btw target date and current date, in seconds
  if (timediff<0){ //if time is up
    this.timesup=true
    this.container.innerHTML=this.formatresults()
    return
  }
  var oneMinute=60 //minute unit in seconds
  var oneHour=60*60 //hour unit in seconds
  var oneDay=60*60*24 //day unit in seconds
  var dayfield=Math.floor(timediff/oneDay)
  var hourfield=Math.floor((timediff-dayfield*oneDay)/oneHour)
  var minutefield=Math.floor((timediff-dayfield*oneDay-hourfield*oneHour)/oneMinute)
  var secondfield=Math.floor((timediff-dayfield*oneDay-hourfield*oneHour-minutefield*oneMinute))


  if (this.baseunit=="hours"){ //if base unit is hours, set "hourfield" to be topmost level
    hourfield=dayfield*24+hourfield
    dayfield="n/a"
  }  
	
  
  else if (this.baseunit=="minutes"){ //if base unit is minutes, set "minutefield" to be topmost level
    minutefield=dayfield*24*60+hourfield*60+minutefield
    dayfield=hourfield="n/a"
  }
  	
	  
  else if (this.baseunit=="seconds"){ //if base unit is seconds, set "secondfield" to be topmost level
    var secondfield=timediff
    dayfield=hourfield=minutefield="n/a"
  }

 if(hourfield < 10) { hourfield = "0" + hourfield; }
if(minutefield < 10) { minutefield = "0" + minutefield; }
if(secondfield < 10) { secondfield = "0" + secondfield; }


  this.container.innerHTML=this.formatresults(dayfield, hourfield, minutefield, secondfield)
  setTimeout(function(){thisobj.showresults()}, 1000) //update results every second  
}


function formatresults(){
  if (this.timesup==false){
    var displaystring= "" 
          + arguments[0] + ":"
          + arguments[1] + ":"
          + arguments[2] + ":"
          + arguments[3] + ""    
  } else{
    var displaystring="0:00:00:00"
  }
  return displaystring
}