/* Checks a string to see if its valid */
function chkdate( datefield )
{
    var strDate;
    var strDateArray;
    var strDay;
    var strMonth;
    var strYear;
    var intday;
    var intMonth;
    var intYear;
    var booFound = false;
    var strSeparatorArray = new Array("-"," ","/",".");
    var intElementNr;
    var err = 0;
    var strMonthArray = new Array(12);
    strMonthArray[0] = "Jan";
    strMonthArray[1] = "Feb";
    strMonthArray[2] = "Mar";
    strMonthArray[3] = "Apr";
    strMonthArray[4] = "May";
    strMonthArray[5] = "Jun";
    strMonthArray[6] = "Jul";
    strMonthArray[7] = "Aug";
    strMonthArray[8] = "Sep";
    strMonthArray[9] = "Oct";
    strMonthArray[10] = "Nov";
    strMonthArray[11] = "Dec";
    var strFullMonthArray = new Array(12);
    strFullMonthArray[0] = "January";
    strFullMonthArray[1] = "February";
    strFullMonthArray[2] = "March";
    strFullMonthArray[3] = "April";
    strFullMonthArray[4] = "May";
    strFullMonthArray[5] = "June";
    strFullMonthArray[6] = "July";
    strFullMonthArray[7] = "August";
    strFullMonthArray[8] = "September";
    strFullMonthArray[9] = "October";
    strFullMonthArray[10] = "November";
    strFullMonthArray[11] = "December";
    strDate = datefield.value;
    
    if (strDate.length < 1 )
        return true;
    
    
    for( intElementNr = 0; intElementNr < strSeparatorArray.length; intElementNr++ )
    {
        if( strDate.indexOf( strSeparatorArray[intElementNr] ) != -1 ) 
        {
            strDateArray = strDate.split( strSeparatorArray[intElementNr] );
            if( strDateArray.length != 3 )
            {
                err = 1;
                return false;
            }
            else
            {
                strDay = strDateArray[0];
                strMonth = strDateArray[1];
                strYear = strDateArray[2];
            }
            booFound = true;
       }
    }
    
    if( booFound == false )
    {
        if( strDate.length > 5 ) 
        {
            strDay = strDate.substr(0, 2);
            strMonth = strDate.substr(2, 2);
            strYear = strDate.substr(4);
        }
        else
            return false;
    }
    
    if (strYear.length == 2)
    {
        if( strYear < 50 )
            strYear = '20' + strYear;
        else
            strYear = '19' + strYear;
    }
    
    intday = parseInt( strDay, 10 );
    if (isNaN(intday)) 
    {
        err = 2;
        return false;
    }
    
    intMonth = parseInt(strMonth, 10);
    if (isNaN(intMonth))
    {
        for (i = 0;i<12;i++)
        {
            if (strMonth.toUpperCase() == strMonthArray[i].toUpperCase() || strMonth.toUpperCase() == strFullMonthArray[i].toUpperCase())
            {
                intMonth = i+1;
                strMonth = strMonthArray[i];
                i = 12;
            }
        }
        if (isNaN(intMonth))
        {
            err = 3;
            return false;
        }
    }
    
    intYear = parseInt(strYear, 10);
    if(isNaN(intYear))
    {
        err = 4;
        return false;
    }
    
    if (intMonth>12 || intMonth<1)
    {
        err = 5;
        return false;
    }
    
    if((intMonth == 1 || intMonth == 3 || intMonth == 5 || intMonth == 7 || intMonth == 8 || intMonth == 10 || intMonth == 12) && 
        (intday > 31 || intday < 1)) 
    {
        err = 6;
        return false;
    }
    
    if((intMonth == 4 || intMonth == 6 || intMonth == 9 || intMonth == 11) && (intday > 30 || intday < 1))
    {
        err = 7;
        return false;
    }
    
    if(intMonth == 2)
    {
        if(intday < 1)
        {
            err = 8;
            return false;
        }
        
        if(LeapYear(intYear) == true)
        {
            if(intday > 29)
            {
                err = 9;
                return false;
            }
        }
        else 
        {
            if (intday > 28)
            {
                err = 10;
                return false;
            }
        }
    }
    datefield.value = fmtNum( intday, 2 ) + "/" + fmtNum( intMonth, 2 ) + "/" + strYear;
    return true;
}

function LeapYear(intYear)
{
    if (intYear % 100 == 0)
    {
        if (intYear % 400 == 0)
            return true;
    }
    else 
    {
        if ((intYear % 4) == 0)
            return true;
    }
    return false;
}

function fmtNum( number, width )
{
    var str = number + "";
    for( var i = str.length; i < width; ++i )
        str = "0" + str;
        
    return str;
}