Need to change author name(created by) in a SharePoint Site

PowerShell command to check the current author name : 

$allsite=get-spsite “Sitename”

$allsite|get-spweb -limit all|foreach-object{ $_.url, $_.author, $_.created} | out-file  -FilePath "e:kast.txt"

$allsite.dispose()

PowerShell to update the author name :

$web = get-spweb http://Your-Site 

$newAuthor = $web.EnsureUser("NewAuthor_LoginName") 

$web.Author = $newAuthor 

$web.Update()