How Can LibreOffice Convert Milliseconds To Timestamp Or DateTime?

Does LibreOffice or some plugins have a generic or standard way to convert milliseconds back into timestamps?

I had converted timestamps into milliseconds because I didn’t find a built-in way to naturally handle a standard time format. But now for real people, I want to convert that time easily back into rationally readable time. Otherwise, does LibreOffice have a way to auto-interpolate dates and 24-hour time like MS-Office Excel or Google-Suite Sheets?