Postgresql – XML- Processing xpath with date comparission

I have ingested XML file in Postgresql DB and I trying to perform XPATH operation on the field with date comparison but it is not working. From Postgresql official site I found out that Postgresql uses Xpath1 and Xpath1 does not support date comparison. I tried changing my Xpath query to use string based comparison but still it is not matching.

Input Xpath:

//val:key[@modifiedDate>"2024-06-06"]

Since Direct date comparison is not available in Xpath1 I tried String based comparison.

Converted Xpath:

//val:key[substring(@modifiedDate, 1, 10) > "2024-06-06"]

But this XPath is also not matching even though there is a matching Xpath. How should I frame my Xpath to match the field with date compaission.

The sample structure of XML ingested in table.

<root>
    <val:key modifiedDate="2024-06-07T12:34:56">Key1</val:key>
    <val:key modifiedDate="2024-06-05T08:21:00">Key2</val:key>
    <val:key modifiedDate="2024-06-10T14:22:33">Key3</val:key>
    <val:key modifiedDate="2024-06-06T09:00:00">Key4</val:key>
</root>

The expected result is we should be able to match this XML becuase it xpaths <val:key modifiedDate="2024-06-07T12:34:56">Key1</val:key> and <val:key modifiedDate="2024-06-10T14:22:33">Key3</val:key>, as their modifiedDate attributes start with dates later than "2024-06-06".

SQL Query for reproducing the problem:

CREATE TABLE xml_data (
    id SERIAL PRIMARY KEY,
    document XML
);

INSERT INTO xml_data (document)
VALUES ('<root>
            <val:key modifiedDate="2024-06-07T12:34:56">Key1</val:key>
            <val:key modifiedDate="2024-06-05T08:21:00">Key2</val:key>
            <val:key modifiedDate="2024-06-10T14:22:33">Key3</val:key>
            <val:key modifiedDate="2024-06-06T09:00:00">Key4</val:key>
        </root>');

Query to filter data:

SELECT 
    id, document
FROM 
    xml_data
WHERE 
    xpath_exists('//val:key[substring(@modifiedDate, 1, 10) > "2024-06-06"]', document);