Update a users name in SharePoint

When a user has a name change in Active Directory, the User Profile Service does not update the information in SharePoint as seen on the userdisp.aspx page.  You can also see this when viewing list/library entries by the user.  The Created By field will still display their old name.  The following PowerShell command will force an update from AD to SharePoint.

Set-SPUser -Identity 'contoso\UserName' –SyncFromAD –Web https://contoso.portal.com


Reference:  Set-SPUser in TechNet.