cpqDaPhyDrvTime gives a relative timestamp, in hours the physical drive has been spinning since it was initialized for monitoring, showing when a given error log entry occurred. This lets an admin sequence error log entries in time and see whether errors are clustering during a particular period of the drive's operational life. For example, an admin noticing several error log entries all clustered around the same reference-hour value would suspect a specific event, like a power glitch, that affected the drive at that point in time.