change the format of date time from USA to AU

<asp:TextBox ID="txtQRequestDate" runat="server" Width="160px" AutoPostBack="false"></asp:TextBox>
                            <em style="vertical-align: bottom; text-align: left;">
                                <img src="Images/calandar.png" onclick="showCalendarControl(document.getElementById('<%=txtQRequestDate.ClientID %>'))"
                                    align="middle" id="IMG1" />
                            </em>

function positionInfo(object) {
    var p_elm = object;
    this.getElementLeft = getElementLeft;
    function getElementLeft() {
        var x = 0;
        var elm;
        if (typeof (p_elm) == "object") {
            elm = p_elm;
        } else {
            elm = document.getElementById(p_elm);
        }
        while (elm != null) {
            x += elm.offsetLeft;
            elm = elm.offsetParent;
        }
        return parseInt(x);
    }
    this.getElementWidth = getElementWidth;
    function getElementWidth() {
        var elm;
        if (typeof (p_elm) == "object") {
            elm = p_elm;
        } else {
            elm = document.getElementById(p_elm);
        }
        return parseInt(elm.offsetWidth);
    }
    this.getElementRight = getElementRight;
    function getElementRight() {
        return getElementLeft(p_elm) + getElementWidth(p_elm);
    }
    this.getElementTop = getElementTop;
    function getElementTop() {
        var y = 0;
        var elm;
        if (typeof (p_elm) == "object") {
            elm = p_elm;
        } else {
            elm = document.getElementById(p_elm);
        }
        while (elm != null) {
            y += elm.offsetTop;
            elm = elm.offsetParent;
        }
        return parseInt(y);
    }
    this.getElementHeight = getElementHeight;
    function getElementHeight() {
        var elm;
        if (typeof (p_elm) == "object") {
            elm = p_elm;
        } else {
            elm = document.getElementById(p_elm);
        }
        return parseInt(elm.offsetHeight);
    }
    this.getElementBottom = getElementBottom;
    function getElementBottom() {
        return getElementTop(p_elm) + getElementHeight(p_elm);
    }
}
function CalendarControl() {
    var calendarId = 'CalendarControl';
    var currentYear = 0;
    var currentMonth = 0;
    var currentDay = 0;
    var selectedYear = 0;
    var selectedMonth = 0;
    var selectedDay = 0;
    var months = ['January', 'February', 'March', 'April', 'May', 'June', 'July', 'August', 'September', 'October', 'November', 'December'];
    var dateField = null;
    function getProperty(p_property) {
        var p_elm = calendarId;
        var elm = null;
        if (typeof (p_elm) == "object") {
            elm = p_elm;
        } else {
            elm = document.getElementById(p_elm);
        }
        if (elm != null) {
            if (elm.style) {
                elm = elm.style;
                if (elm[p_property]) {
                    return elm[p_property];
                } else {
                    return null;
                }
            } else {
                return null;
            }
        }
    }
    function setElementProperty(p_property, p_value, p_elmId) {
        var p_elm = p_elmId;
        var elm = null;
        if (typeof (p_elm) == "object") {
            elm = p_elm;
        } else {
            elm = document.getElementById(p_elm);
        }
        if ((elm != null) && (elm.style != null)) {
            elm = elm.style;
            elm[p_property] = p_value;
        }
    }
    function setProperty(p_property, p_value) {
        setElementProperty(p_property, p_value, calendarId);
    }
    function getDaysInMonth(year, month) {
        return [31, ((!(year % 4) && ((year % 100) || !(year % 400))) ? 29 : 28), 31, 30, 31, 30, 31, 31, 30, 31, 30, 31][month - 1];
    }
    function getDayOfWeek(year, month, day) {
        var date = new Date(year, month - 1, day)
        return date.getDay();
    }
    this.setDate = setDate;
    function setDate(year, month, day) {
        if (dateField) {
            if (month < 10) { month = "0" + month; }
            if (day < 10) { day = "0" + day; }
                  var dateString = month+"/"+day+"/"+year;
           //  var dateString = day + "/" + month + "/" + year;
            dateField.value = dateString;
            hide();
        }
        return;
    }
    this.changeMonth = changeMonth;
    function changeMonth(change) {
        currentMonth += change;
        currentDay = 0;
        if (currentMonth > 12) {
            currentMonth = 1;
            currentYear++;
        } else if (currentMonth < 1) {
            currentMonth = 12;
            currentYear--;
        }
        calendar = document.getElementById(calendarId);
        calendar.innerHTML = calendarDrawTable();
    }
    this.changeYear = changeYear;
    function changeYear(change) {
        currentYear += change;
        currentDay = 0;
        calendar = document.getElementById(calendarId);
        calendar.innerHTML = calendarDrawTable();
    }
    function getCurrentYear() {
        var year = new Date().getYear();
        if (year < 1900) year += 1900;
        return year;
    }
    function getCurrentMonth() {
        return new Date().getMonth() + 1;
    }
    function getCurrentDay() {
        return new Date().getDate();
    }
    function calendarDrawTable() {
        var dayOfMonth = 1;
        var validDay = 0;
        var startDayOfWeek = getDayOfWeek(currentYear, currentMonth, dayOfMonth);
        var daysInMonth = getDaysInMonth(currentYear, currentMonth);
        var css_class = null; //CSS class for each day
        var table = "<table cellspacing='0' cellpadding='0' border='0'>";
        table = table + "<tr class='header'>";
        table = table + "  <td colspan='2' class='previous'><a href='javascript:changeCalendarControlMonth(-1);'>&lt;</a> <a href='javascript:changeCalendarControlYear(-1);'>&laquo;</a></td>";
        table = table + "  <td colspan='3' class='title'>" + months[currentMonth - 1] + "<br>" + currentYear + "</td>";
        table = table + "  <td colspan='2' class='next'><a href='javascript:changeCalendarControlYear(1);'>&raquo;</a> <a href='javascript:changeCalendarControlMonth(1);'>&gt;</a></td>";
        table = table + "</tr>";
        table = table + "<tr><th>S</th><th>M</th><th>T</th><th>W</th><th>T</th><th>F</th><th>S</th></tr>";
        for (var week = 0; week < 6; week++) {
            table = table + "<tr>";
            for (var dayOfWeek = 0; dayOfWeek < 7; dayOfWeek++) {
                if (week == 0 && startDayOfWeek == dayOfWeek) {
                    validDay = 1;
                } else if (validDay == 1 && dayOfMonth > daysInMonth) {
                    validDay = 0;
                }
                if (validDay) {
                    if (dayOfMonth == selectedDay && currentYear == selectedYear && currentMonth == selectedMonth) {
                        css_class = 'current';
                    } else if (dayOfWeek == 0 || dayOfWeek == 6) {
                        css_class = 'weekend';
                    } else {
                        css_class = 'weekday';
                    }
                    table = table + "<td><a class='" + css_class + "' href=\"javascript:setCalendarControlDate(" + currentYear + "," + currentMonth + "," + dayOfMonth + ")\">" + dayOfMonth + "</a></td>";
                    dayOfMonth++;
                } else {
                    table = table + "<td class='empty'>&nbsp;</td>";
                }
            }
            table = table + "</tr>";
        }
        table = table + "<tr class='header'><th colspan='7' style='padding: 3px;'><a href='javascript:hideCalendarControl();'>Close</a></td></tr>";
        table = table + "</table>";
        return table;
    }
    this.show = show;
    function show(field) {
        // If the calendar is visible F associated with
        // this field do not do anything.
        if (dateField == field) {
            return;
        } else {
            dateField = field;
        }
        if (dateField) {
            try {
                var dateString = new String(dateField.value);
                var dateParts = dateString.split("/");
                selectedMonth = parseInt(dateParts[0], 10);
                selectedDay = parseInt(dateParts[1], 10);
                selectedYear = parseInt(dateParts[2], 10);
            }
            catch (e) { }
        }
        if (!(selectedYear && selectedMonth && selectedDay)) {
            selectedMonth = getCurrentMonth();
            selectedDay = getCurrentDay();
            selectedYear = getCurrentYear();
        }
        currentMonth = selectedMonth;
        currentDay = selectedDay;
        currentYear = selectedYear;
        if (document.getElementById) {
            calendar = document.getElementById(calendarId);
            calendar.innerHTML = calendarDrawTable(currentYear, currentMonth);
            setElementProperty('display', 'block', 'CalendarControlIFrame');
            setProperty('display', 'block');
            var fieldPos = new positionInfo(dateField);
            var calendarPos = new positionInfo(calendarId);
            var x = fieldPos.getElementLeft();
            var y = fieldPos.getElementBottom();
            setProperty('left', x + "px");
            setProperty('top', y + "px");
            setElementProperty('left', x + "px", 'CalendarControlIFrame');
            setElementProperty('top', y + "px", 'CalendarControlIFrame');
            setElementProperty('width', calendarPos.getElementWidth() + "px", 'CalendarControlIFrame');
            setElementProperty('height', calendarPos.getElementHeight() + "px", 'CalendarControlIFrame');
        }
    }
    this.hide = hide;
    function hide() {
        if (dateField) {
            setProperty('display', 'none');
            setElementProperty('display', 'none', 'CalendarControlIFrame');
            dateField = null;
        }
    }
}
var calendarControl = new CalendarControl();
function showCalendarControl(textField) {
    calendarControl.show(textField);
}
function hideCalendarControl() {
    calendarControl.hide();
}
function setCalendarControlDate(year, month, day) {
    calendarControl.setDate(year, month, day);
}
function changeCalendarControlYear(change) {
    calendarControl.changeYear(change);
}
function changeCalendarControlMonth(change) {
    calendarControl.changeMonth(change);
}
document.write("<iframe id='CalendarControlIFrame' src='javascript:false;' frameBorder='0' scrolling='no'></iframe>");
document.write("<div id='CalendarControl'></div>");