为什么倒计时是 00:00:00

/*代码是这样的 */

/**
 * Created by Administrator on 2015/3/25.
 */
var WINDOW_WIDTH = 1024;
var WINDOW_HEIGHT = 768;
var RADIUS = 8;
var MARGIN_TOP = 60;
var MARGIN_LEFT = 30;


const endTime = new Date(2014,3,26,18,47,52);
var curshowTimeseconds = 0

window.onload = function(){

    var canvas = document.getElementById("canvas");
    var context = canvas.getContext("2d");

    canvas.width = WINDOW_WIDTH;
    canvas.height = WINDOW_HEIGHT;

    curshowTimeseconds = getCurrentShowTimeSeconds()

    render( context )
}

function getCurrentShowTimeSeconds() {
    var curTime = new Date();
    var ret = endTime.getTime() - curTime.getTime();
    ret = Math.round( ret/1000 )

    return ret >= 0 ? ret : 0;
}

function render( cxt ){
    var hours = parseInt( curshowTimeseconds / 3600)
    var minutes = parseInt( (curshowTimeseconds - hours * 3600)/60 )
    var seconds = curshowTimeseconds % 60

    renderDigit( MARGIN_LEFT , MARGIN_TOP , parseInt(hours/10) , cxt )
    renderDigit( MARGIN_LEFT + 15*(RADIUS+1) , MARGIN_TOP , parseInt(hours%10) , cxt )
    renderDigit( MARGIN_LEFT + 30*(RADIUS+1) , MARGIN_TOP , 10 , cxt )
    renderDigit( MARGIN_LEFT + 39*(RADIUS+1) , MARGIN_TOP , parseInt(minutes/10) , cxt )
    renderDigit( MARGIN_LEFT + 54*(RADIUS+1) , MARGIN_TOP , parseInt(minutes%10) , cxt )
    renderDigit( MARGIN_LEFT + 69*(RADIUS+1) , MARGIN_TOP , 10 , cxt )
    renderDigit( MARGIN_LEFT + 78*(RADIUS+1) , MARGIN_TOP , parseInt(seconds/10) , cxt )
    renderDigit( MARGIN_LEFT + 93*(RADIUS+1) , MARGIN_TOP , parseInt(seconds%10) , cxt )
}
function renderDigit( x , y , num , cxt ){

    cxt.fillStyle = "rgb(0,102,153)";

    for( var i = 0 ; i < digit[num].length ; i ++ )
        for( var j = 0 ; j < digit[num][i].length ; j ++ )
           if( digit[num][i][j] == 1 ){
               cxt.beginPath();
               cxt.arc( x+j*2*(RADIUS+1)+(RADIUS+1) , y+i*2*(RADIUS+1)+(RADIUS+1) , RADIUS , 0 , 2*Math.PI )
               cxt.closePath()

               cxt.fill()
           }
}