Check the thread
https://www-secure.symantec.com/connect/forums/report-show-software-install-date
https://www-secure.symantec.com/connect/forums/report-installed-software-products-and-install-date
##edit##
SELECT vc.Name, sp.Name, inst.InstallDate
FROM vRM_Computer_Item vc
JOIN Inv_InstalledSoftware inst
ON inst._ResourceGuid = vc.Guid
AND inst.InstallFlag = 1
JOIN ResourceAssociation ra
ON ra.ChildResourceGuid = inst._SoftwareComponentGuid
AND ra.ResourceAssociationTypeGuid = '9D67B0C6-BEFF-4FCD-86C1-4A40028FE483'
JOIN vSoftwareProduct sp
ON sp.Guid = ra.ParentResourceGuid
ORDER BY vc.Name ASC