// 
// JavaScript Date functions
// 
// isDate(year, month, day) checks for a valid date, returns false if invalid
//

var daysInMonth = new Array(12);
daysInMonth[1] = 31;
daysInMonth[2] = 29;   // must programmatically check this
daysInMonth[3] = 31;
daysInMonth[4] = 30;
daysInMonth[5] = 31;
daysInMonth[6] = 30;
daysInMonth[7] = 31;
daysInMonth[8] = 31;
daysInMonth[9] = 30;
daysInMonth[10] = 31;
daysInMonth[11] = 30;
daysInMonth[12] = 31;


function daysInFebruary (year)
{   // February has 29 days in any year evenly divisible by four,
    // EXCEPT for centurial years which are not also divisible by 400.
    return (  ((year % 4 == 0) && ( (!(year % 100 == 0)) || (year % 400 == 0) ) ) ? 29 : 28 );
}



// isDate (STRING year, STRING month, STRING day)
//
// isDate returns true if string arguments year, month, and day 
// form a valid date.
// 

function isDate (year, month, day)
{   
    // Explicitly change type to integer to make code work in both
    // JavaScript 1.1 and JavaScript 1.2.
    if ( isNaN(year) || isNaN(month) || isNaN(day) )
		return false;
    var intYear = parseInt(year,10);
    var intMonth = parseInt(month,10);
    var intDay = parseInt(day,10);

    // valid years from 1000 up to 9999	
    if (year.length != 4) return false;	     

    if (intMonth < 1 || intMonth > 12) return false;
	
    // catch invalid days, except for February
    if (intDay < 1 || intDay > daysInMonth[intMonth]) return false; 

    if ((intMonth == 2) && (intDay > daysInFebruary(intYear))) return false;

    return true;
}

function isDateString(strDate)
{
    var arrDate = strDate.split("-");
    return isDate(arrDate[2], arrDate[1], arrDate[0]);
}