inserting mysql date field into MySQL Database - php

Question

I'm having an issue submitting a form into a database once I have added a Submitted_Date field.
The errors are as follows:
Fatal error: Uncaught mysqli_sql_exception: Incorrect date value:
'2022' for column 'Submitted_Date'
mysqli_sql_exception: Incorrect date value: '2022' for column
'Submitted_Date'
Prior to adding in $Submitted_Date = date('Y-m-d', strtotime($_POST['Submitted_Date'])); I was also getting an error for incorrect listed fields on the binding.
The Submitted_Date field is a date input field so needs to be handled as 'NULL' value if a date has not been entered. Instead I also get a
'Incorrect date value: '1970'
Any help would be great. Thanks.
<?php
if (isset($_POST['submit'])) {
$sql = $conn->prepare("UPDATE orders SET Publisher_Email=? , Client_Name=? , Submitted_Date=? WHERE PC_Job_Number=?
");
$Publisher_Email = $_POST['Publisher_Email'];
$Client_Name = $_POST['Client_Name'];
$Submitted_Date = date('Y-m-d', strtotime($_POST['Submitted_Date']));
$sql->bind_param("ssii", $Publisher_Email, $Client_Name, $Submitted_Date, $_GET["PC_Job_Number"]);
if (empty($Submitted_Date)) {
$Submitted_Date = "NULL";
}
if($sql->execute()) {
$success_message = "Edited Successfully";
} else {
$error_message = "Problem in Editing Record";
}
}
$sql = $conn->prepare("SELECT * FROM orders WHERE PC_Job_Number=?");
$sql->bind_param("i",$_GET["PC_Job_Number"]);
$sql->execute();
$result = $sql->get_result();
if ($result->num_rows > 0) {
$row = $result->fetch_assoc();
}
$conn->close();
?>