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According to Microsoft's official documentation, the properties of the Web Applicaiton are stored in the SPWeb class, but the properties of the SPWeb only record the date when the web application was created, not the creator. So, we can only get the creation date of the web application.
Reference: SPWeb properties.
You can run the following command to get the creation date of the web application:
$wa = Get-SPWebApplication https://sharepointsitename.com
$sites = $wa.Sites
foreach ($site in $sites)
{
$web = $site.rootweb
write-host $web.Url, $web.created
$site.dispose()
}
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