This PmTimeDate reports when the current, shorter sample interval (the same cadence configured via cienaCesPmIntervalProfileSampleInterval) began, per its DESCRIPTION, distinct from the longer Adjustment Interval tracked by IntervalStartTime. Several sample intervals accumulate inside a single Adjustment Interval, so this timestamp is what you'd use to line up a single suspicious sample reading with the exact short window it came from, rather than only knowing which multi-sample Adjustment Interval it fell within. For example, with a 5-minute sample interval inside a 1-hour Adjustment Interval, this timestamp advances every 5 minutes even while IntervalStartTime stays fixed for the full hour.