Reverse jquery countdown timer

Question

I have this countdown timer script that shows the remaining time until the X day. Now that X day has passed the countdown shows zero values. How do I go about making this in reverse showing the elapse time since X day instead?

// Number of seconds in every time division
var days    = 24*60*60,
    hours   = 60*60,
    minutes = 60;

// Creating the plugin
$.fn.countdown = function(prop){

    var options = $.extend({
        callback    : function(){},
        timestamp   : 0
    },prop);

    var left, d, h, m, s, positions;

    // Initialize the plugin
    init(this, options);

    positions = this.find('.position');

    (function tick(){

        // Time left
        left = Math.floor((options.timestamp - (new Date())) / 1000);

        if(left < 0){
            left = 0;
        }

        // Number of days left
        d = Math.floor(left / days);
        updateDuo(0, 1, d);
        left -= d*days;

        // Number of hours left
        h = Math.floor(left / hours);
        updateDuo(2, 3, h);
        left -= h*hours;

        // Number of minutes left
        m = Math.floor(left / minutes);
        updateDuo(4, 5, m);
        left -= m*minutes;

        // Number of seconds left
        s = left;
        updateDuo(6, 7, s);

        // Calling an optional user supplied callback
        options.callback(d, h, m, s);

        // Scheduling another call of this function in 1s
        setTimeout(tick, 1000);
    })();

    // This function updates two digit positions at once
    function updateDuo(minor,major,value){
        switchDigit(positions.eq(minor),Math.floor(value/10)%10);
        switchDigit(positions.eq(major),value%10);
    }

    return this;
};


function init(elem, options){
    elem.addClass('countdownHolder');

    // Creating the markup inside the container
    $.each(['Days','Hours','Minutes','Seconds'],function(i){
                    $('<span class="count'+this+'">'+
                            '<span class="position">'+
                                    '<span class="digit static">0</span>'+
                            '</span>'+
                            '<span class="position">'+
                                    '<span class="digit static">0</span>'+
                            '</span>'+
                    '</span>').appendTo(elem);

        if(this!="Seconds"){
            elem.append('<span class="countDiv countDiv'+i+'"></span>');
        }
    });

}

// Creates an animated transition between the two numbers
function switchDigit(position,number){

    var digit = position.find('.digit')

    if(digit.is(':animated')){
        return false;
    }

    if(position.data('digit') == number){
        // We are already showing this number
        return false;
    }

    position.data('digit', number);

    var replacement = $('<span>',{
        'class':'digit',
        css:{
            top:'-2.1em',
            opacity:0
        },
        html:number
    });

    // The .static class is added when the animation
    // completes. This makes it run smoother.

    digit
        .before(replacement)
        .removeClass('static')
        .animate({top:'2.5em',opacity:0},'fast',function(){
            digit.remove();
        })

    replacement
        .delay(100)
        .animate({top:0,opacity:1},'fast',function(){
            replacement.addClass('static');
        });
}

Answer 1

I think if you remove these lines it should keep going. This will show negative time so you will need to modify it a bit to say elapsed instead of time to but can't see that code here.

if(left < 0){
    left = 0;
}

If you want it to stay positive and start counting up then you could change this:

left = Math.floor((options.timestamp - (new Date())) / 1000);

to this:

left = Math.abs(Math.floor((options.timestamp - (new Date())) / 1000));