var dtCh = "/";
var minYear = 2008;
var maxYear = 2100;

function isInteger(s) {
    var i;
    for (i = 0; i < s.length; i++) {
        var c = s.charAt(i);
        if (((c < "0") || (c > "9"))) return false;
    }
    return true;
}

function stripCharsInBag(s, bag) {
    var i;
    var returnString = "";
    for (i = 0; i < s.length; i++) {
        var c = s.charAt(i);
        if (bag.indexOf(c) == -1) returnString += c;
    }
    return returnString;
}

function daysInFebruary(year) {
    return (((year % 4 == 0) && ((!(year % 100 == 0)) || (year % 400 == 0))) ? 29 : 28);
}

function DaysArray(n) {
    for (var i = 1; i <= n; i++) {
        this[i] = 31;
        if (i == 4 || i == 6 || i == 9 || i == 11) this[i] = 30;
        if (i == 2) this[i] = 29;
    }
    return this
}

function isDate(dtStr) {
    var daysInMonth = DaysArray(12);
    var pos1 = dtStr.indexOf(dtCh);
    var pos2 = dtStr.indexOf(dtCh, pos1 + 1);
    var strDay = dtStr.substring(0, pos1);
    var strMonth = dtStr.substring(pos1 + 1, pos2);
    var strYear = dtStr.substring(pos2 + 1);
    strYr = strYear;
    if (strDay.charAt(0) == "0" && strDay.length > 1) strDay = strDay.substring(1);
    if (strMonth.charAt(0) == "0" && strMonth.length > 1) strMonth = strMonth.substring(1);
    for (var i = 1; i <= 3; i++) {
        if (strYr.charAt(0) == "0" && strYr.length > 1) strYr = strYr.substring(1);
    }
    month = parseInt(strMonth);
    day = parseInt(strDay);
    year = parseInt(strYr);
    if (pos1 == -1 || pos2 == -1) return false; //date format should be : dd/mm/yyyy
    if (strMonth.length < 1 || month < 1 || month > 12) return false; // invalid month
    if (strDay.length < 1 || day < 1 || day > 31 || (month == 2 && day > daysInFebruary(year)) || day > daysInMonth[month]) return false; // invalid day
    if (strYear.length != 4 || year == 0 || year < minYear || year > maxYear) return false; // invalid year
    if (dtStr.indexOf(dtCh, pos2 + 1) != -1 || !isInteger(stripCharsInBag(dtStr, dtCh))) return false; // invalid date

    return true;
}

function FormatYear(datestring) {
    if (datestring.substring(6, 8) == "00")
        return datestring.substring(0, 6) + "20" + datestring.substring(8, 10);
    else
        return datestring;
}

function ValidateDate(datestring) {
    datestring = FormatYear(datestring);
    if (!isDate(datestring))
        return false;
    else {
        var date = ToDate(datestring);
        var now = new Date();
        return date >= now; //Past dates not considered valid.
    }
}

function ValidateDateField(source, args) {
    args.IsValid = ValidateDate(args.Value);
}

function FormatDate(datestring) {
    datestring = FormatYear(datestring);
    if (ValidateDate(datestring)) {
        var parts = datestring.split('/');
        var day = parts.length < 1 ? now.getDate() : parts[0];
        var month = parts.length < 2 ? now.getMonth() : parts[1];
        var year = parts.length < 3 ? now.getFullYear() : parts[2];

        day = day.length == 1 ? "0" + day : day;
        month = month.length == 1 ? "0" + month : month;
        year = year.length == 2 ? "20" + year : year;

        return day + "/" + month + "/" + year;
    }
    else
        return datestring;
}

function ToDate(datestring) {
    var parts = datestring.split('/');
    var now = new Date();
    var day = parts.length < 1 ? now.getDate() : parts[0];
    var month = parts.length < 2 ? now.getMonth() : parts[1];
    var year = parts.length < 3 ? now.getFullYear() : parts[2];

    if (year.length == 0 || year.length == 1 || year.length == 3)
        return null;

    if (year.length == 2)
        year = "20" + year;

    var retval = new Date();
    retval.setFullYear(year);
    retval.setMonth(month - 1);
    retval.setDate(day);
    return retval;
}