Symantec Endpoint Protection uses the LastSuccessfulScanDateTime registry key to record last successful scan completion
[HKEY_LOCAL_MACHINE\SOFTWARE\Symantec\Symantec Endpoint Protection\CurrentVersion\public-opstate]
This registry entry did not get updated when Full, Manual or Active Scan get Aborted.
The LastSuccessfulScanDateTime registry key is used for Date and Time of last successful scan. When the Full, Manual or Active Scan get aborted, it will not update the lastsuccessfulscandatetime registry key. If the scan ran until completion, it will automatically update lastsuccessfulscandatetime registry key with completion time.
List of Scan Aborted Reason