timer.js

$(function($) {

    init_clock();

    setInterval(function() {
        update_clock();
    }, 1000);

    //Inits the clock with date from server
    function init_clock() {
//        $('#datepicker').attr('data-current-time', '08:09:55');
        $('#clock').text($('#datepicker').attr('data-current-time'));
    }

    function update_clock() {
        var splited_time = $('#clock').text().split(':');

        var current_second = parseInt(splited_time[2], 10) + 1;
        var current_minute = parseInt(splited_time[1], 10);
        var current_hour = parseInt(splited_time[0], 10);

        if (current_second > 59) {
            current_second = 0;
            current_minute = current_minute + 1;
        }

        var new_hour = current_hour;
        if (current_minute > 59) {
            current_minute = 0;
            if (current_hour == 12) new_hour = 13;
            else if (current_hour == 23) new_hour = 0;
            else new_hour = current_hour + 1;
        }

        var str_second = current_second.toString();
        var str_minute = current_minute.toString();
        var str_hour = new_hour.toString();

        if (current_second <= 9) str_second = '0' + str_second;  
        if (current_minute <= 9) str_minute = '0' + str_minute;
        if (new_hour <= 9) str_hour = '0' + str_hour;  

        var str_time = str_hour + ':' + str_minute + ':' + str_second;

        $('#clock').text(str_time);
    }
});