Cisco Date of Manufacturing Audit

SELECT TOP 1000000 tblAssets.AssetID,
  tblAssets.AssetName,
  tsysAssetTypes.AssetTypename,
  tsysAssetTypes.AssetTypeIcon10 AS icon,
  tblAssets.IPAddress,
  Serialnumber,
  DATEADD(DAY,7*SUBSTRING(Serialnumber,6,2)-7,
  DATEADD(YEAR,96+SUBSTRING(Serialnumber,4,2),0)) 'Date of Manufacture',
  tblAssets.Lastseen,
  tblAssets.Lasttried
FROM tblAssets
  INNER JOIN tblAssetCustom ON tblAssets.AssetID = tblAssetCustom.AssetID
  INNER JOIN tsysAssetTypes ON tsysAssetTypes.AssetType = tblAssets.Assettype
WHERE tblAssetCustom.State = 1 AND Manufacturer LIKE '%cisco%' AND Serialnumber <> ''