Date Validation JS

//Date Validation
/*It validate the date in MM/DD/YYYY format. the argument DateValue is the id of the textbox. required defines that
this field is to be filled not not. it takes two value. one is true (Must filled). false means optional.*/
function validateDate(DateValue, required)
{
var date = DateValue.value;
var RegExPattern = /^(?=\d)(?:(?:(?:(?:(?:0?[13578]1[02])(\/-\.)31)\1(?:(?:0?[1,3-9]1[0-2])(\/-\.)(?:2930)\2))(?:(?:1[6-9][2-9]\d)?\d{2})(?:0?2(\/-\.)29\3(?:(?:(?:1[6-9][2-9]\d)?(?:0[48][2468][048][13579][26])(?:(?:16[2468][048][3579][26])00))))(?:(?:0?[1-9])(?:1[0-2]))(\/-\.)(?:0?[1-9]1\d2[0-8])\4(?:(?:1[6-9][2-9]\d)?\d{2}))($\ (?=\d)))?(((0?[1-9]1[012])(:[0-5]\d){0,2}(\ [AP]M))([01]\d2[0-3])(:[0-5]\d){1,2})?$/;
if(required == true)
{
if(date == '' date == null date == "")
{
alert("Enter the Date");
DateValue.select();
DateValue.focus();
return false;
}
else
{
if (date.match(RegExPattern))
{
return true;
}
else
{
alert("Enter a valid date as mm/dd/yyyy");
DateValue.select();
DateValue.focus();
return false;
}
}
}
else
{
if(date == '' date == null date == "")
{
return true;
}
else
{
if (date.match(RegExPattern))
{
return true;
}
else
{
alert("Enter a valid date as mm/dd/yyyy");
DateValue.select();
DateValue.focus();
return false;
}
}
}
}