Substitutes built in Date object with our own to support time shifting

TimeMachine.js

/*jslint strict: false */
// beware TOXIC HACK
(function ($) {
    // footer contains UpdatePanel with server time
    function getApplicationTime() {
        var regex = /.*(\d{4})-(\d{2})-(\d{2}) (\d{2}):(\d{2}):(\d{2}).*/g,
            m = regex.exec($('#ctl00_UpdateLastAsync').text()), i;

        for (i = 1; i <= 6; i = i + 1) {
            m[i] = parseInt(m[i], 10);
        }

        return (new Date(m[1], m[2] - 1, m[3], m[4], m[5], m[6], 0)).getTime();
    }

    function copyProperties(source, target) {
        for (property in source) {
            if (source.hasOwnProperty(property)) {
                target[property] = source[property];
            }
        }
    }

    function substituteJavaScriptDate() {
        try {
            var OriginalDateClass = Date,
                appTime = getApplicationTime(),
                clientTime = (new Date()).getTime(),
                timeDelta = appTime - clientTime,
                NewDateClass = function () {
                    var args = [0, 1, 1, 0, 0, 0, 0], newDate, i;

                    // workaround: apply(this, arguments) doesn't work on Date constructor
                    if (arguments.length > 0) {
                        if (arguments.length === 1) {
                            // string or ticks
                            newDate = new OriginalDateClass(arguments[0]);
                        }
                        else {
                            for (i = 0; i < arguments.length; i = i + 1) {
                                args[i] = arguments[i];
                            }

                            newDate = new OriginalDateClass(
                                args[0], args[1], args[2], args[3], args[4], args[5], args[6]);
                        }
                    }
                    else {
                        newDate = new OriginalDateClass();
                        try {
                            newDate.setTime(newDate.getTime() + timeDelta);
                        }
                        catch (e) { }
                    }

                    return newDate;
                };

            copyProperties(Date, NewDateClass);
            NewDateClass.prototype.__proto__ = Date;
            Date = NewDateClass;
        }
        catch (e) {
            /* no changes */
        }
    }

    $(substituteJavaScriptDate);
} (jQuery));