function isDate(day, month, year)
{
  var monthLength = new Array(31,28,31,30,31,30,31,31,30,31,30,31);

  if (!day || !month || !year)
    return false;
	
  // check for bisestile year
  if (year/4 == parseInt(year/4))
    monthLength[1] = 29;

  if (month < 1 || month > 12)
    return false;

  if (day > monthLength[month-1])
    return false;
  
  return true;
}