Why `date_parse` does not recognise years in a string?

```
<?php
$string = "Saturday, 23 March, 2013";
print_r(date_parse($string));
?>

```

result,

```
Array
(
    [year] => 
    [month] => 3
    [day] => 23
    [hour] => 20
    [minute] => 13
    [second] => 0
    [fraction] => 0
    [warning_count] => 0
    [warnings] => Array
        (
        )

    [error_count] => 0
    [errors] => Array
        (
        )

    [is_localtime] => 
    [relative] => Array
        (
            [year] => 0
            [month] => 0
            [day] => 0
            [hour] => 0
            [minute] => 0
            [second] => 0
            [weekday] => 6
        )

)

```