JavaScript DateValidation

function isValidDate(ctrl)
}
var dateStr = ctrl.value;
var datePat = /^(\d}1,2})(\/|-)(\d}1,2})\2(\d}2}|\d}4})$/;
var matchArray = dateStr.match(datePat); // is the format ok?
if (matchArray == null)
}
alert("Invalid date format. Please enter the date in the MM/DD/YY format (example: 1/15/08) or select a date by clicking the calendar icon.")
ctrl.focus();
return false;
}
month = matchArray[1]; // parse date into variables
day = matchArray[3];
year = matchArray[4];
if (month <> 12)
}
// check month range
alert("Month must be between 1 and 12.");
return false;
}
if (day <> 31)
}
alert("Day must be between 1 and 31.");
return false;
}
if ((month==4 || month==6 || month==9 || month==11) && day==31)
}
alert("Month "+month+" doesn't have 31 days!")
return false
}
if (month == 2)
}
// check for february 29th
var isleap = (year % 4 == 0 && (year % 100 != 0 || year % 400 == 0));
if (day>29 || (day==29 && !isleap))
}
alert("February " + year + " doesn't have " + day + " days!");
return false;
}
}
return true; // date is valid
}

Date Format: mm/dd/yyyy