I believe [Client Date] from the Inv_Aex_Ac_Identification table is the local date on the client when the last basic inventory was sent. If your clients only send basic inventory once a day, then last config request or last event received would be a better gauge if your goal is to see what machines are active. However, If you are just wanting to know machines that have been offline for days or weeks, you may not care about time zones or recent activity.
I see you are filtering the results to take out machines with blank serial numbers. This will cause slow processing of the query and you may miss machines that have not run hardware inventory so I replaced it with filtering on only managed machines. This should avoid reporting on machine records imported from AD for example that aren't actually running a client but include the rest.
Here is an updated report with Last Config Request date added and the 'Type' field commented out so you can see how much faster it runs. If you have machines in multiple time zones, this method shows the date / time of the NS when the event was received instead of client time.
SELECT vc.[GUID]
, vc.Name AS 'Computer Name'
, vc.[Domain]
, vc.[IP Address]
, vc.[OS Name]
, vc.[OS Revision]
, cs.Manufacturer
, cs.Model
, cs.[Identifying Number] AS 'Serial Number'
, p.Model AS 'Processor'
, cs.[Total Physical Memory (Bytes)] / 1048576 AS 'RAM (MB)'
, vi.Name AS 'Location'
, vc.[User] AS 'Primary Owner'
, c.[Chassis Package Type]
, ISNULL(s.[String],'Other') [Type]
,( SELECT TOP 1 CC.[StartTime] FROM [evt_ns_client_config_request] CC
WHERE CC.[ResourceGuid] = vc.[Guid]
ORDER BY CC.[StartTime] DESC
) AS [Last Config Request]
FROM vComputer vc
LEFT OUTER JOIN ResourceAssociation loc
ON (loc.ChildResourceGuid = vc.Guid OR loc.ParentResourceGuid = vc.Guid)
AND loc.ResourceAssociationTypeGuid = '05DE450F-39EA-4AAE-8C5F-77817889C27C'
LEFT OUTER JOIN vItem vi
ON loc.ChildResourceGuid = vi.Guid
LEFT OUTER JOIN vHWProcessor p
ON vc.Guid = p._ResourceGuid
INNER JOIN vHWComputerSystem cs
ON vc.Guid = cs._ResourceGuid
INNER JOIN Inv_HW_Chassis c
ON vc.Guid = c._ResourceGuid
LEFT OUTER JOIN String s
ON s.StringRef = 'listitem.chassis.chassistypes.' + CAST(c.[Chassis Package Type] as nvarchar(2))
AND s.Culture=''
WHERE vc.ismanaged = 1
--and cs.[Identifying Number] IS NOT NULL
and vc.[OS Name] NOT LIKE '%server%'
ORDER BY vc.Name