// This function validate a date with the following format
// 	Day/Month/Year with:
//  	Day   1-31 (optional zero on single digits)
//      Month 1-12 (optional zero on single digits)
//      Year  One, Two or four digits
//
// It checks if the format is correct.
// If the format is correct, it also checks for the the date existence
// For example: 29/02/2007 does not exist
//
// @param dateValue A date in string format
// @return validity of the date
// @retvalue true date is valid
// @retvalue false date is invalid
function isDateValid(dateValue)
{
	// Default result is true
	var result = true;
	var dateStr = dateValue.trim();

	// Empty date field is correct
	if (dateStr.length > 0)
	{
		// This regular expression validate the input date format
        // to the following rules;
        //         Day   1-31 (optional zero on single digits)
        //         Month 1-12 (optional zero on single digits)
        //         Year  One, Two or four digits
        //
        //			Or empty field
        //
        // Each date component is captured using the parenthesis. See matcher below
        var dateRegEx = new RegExp("^(0?[1-9]|[1-2][0-9]|3[0-1])/(0?[1-9]|1[0-2])/([0-9]{1,2}|[0-9]{4})$");

		var	matcher  = dateRegEx.exec(dateStr);
		if (matcher != null)
		{
			// The date format is correct...
			// Check that the date is itself correct (for example 29/02/2007 does not exist)
			var day = matcher[1];
			var month = matcher[2];
			var year = matcher[3];

			// If the year is one or two digits then the routine assumes a
            // year belongs in the 21st Century.
            // 0 --> 2000, 1 --> 2001...
			if (year < 100)
			{
				year += 2000;
			}

			// Build a date for validation using the internal native code
			var date = new Date(year, month-1, day);

			// Check that the stored date is the one we entered
			// otherwise, the date was incorrect

			if (date.getDate() != day ||
				date.getMonth() != month-1 ||
				date.getFullYear() != year)
			{
				result = false;
			}
		}
		else
		{
			result = false;
		}
	}

	return result;
}