ช่วยด้วยค่ะ มีปัญหาเรื่องการ insert วันที่ลงฐานข้อมูลค่ะ (datetime) มันขึ้น 1970-01-01 00:00:00

<? session_start();
	if($_SESSION['student_id'] == ""){
		echo "Please Login!";
		exit();
	}
	mysql_connect("localhost","root","1234");
	mysql_select_db("regis");

	if($_POST['password'] != $_POST['conpassword']){
		echo "Password not Match";
		exit();
	}

	
	$sql = "INSERT INTO course (course_name,course_type,course_frequency_per_week,course_day) VALUES ('$_POST[course]','$_POST[coursetype]','$_POST[coursefre]','$_POST[day]')";
	$sqlQuery = mysql_query($sql);
	
	$datein = date('Y-m-d', strtotime($_POST['id_datetime_picker0']));
	$sql1 = "INSERT INTO schedule_course (schedule_datetime) VALUES ('".mysql_real_escape_string($datein)."')";
	$sqlQuery1 = mysql_query($sql1);
	
	
	
	$sqlup= "UPDATE schedule_course SET course_id = '".trim($_POST['course'])."',course_day_id = '".trim($_POST['day'])."'";
    $upquery=mysql_query($sqlup);
	
	if($sql){
		echo "<script language='javascript'> alert(' Course Register Success');
				</script>";
		echo '<script type="text/javascript">window.location = "course.php";</script>';
	}else if($sql1){
		echo "<script language='javascript'> alert(' Course Register Success');
				</script>";
		echo '<script type="text/javascript">window.location = "course.php";</script>';
	}else{
		echo "Error:";
	}
	
	mysql_close();
	?>