This field reports collection start time of the bin, exposed here as cienaCesPmExtendedTxRxStatsBinStartTime. On this Ciena CES port's PM data, this DisplayString timestamp marks exactly when the bin began accumulating, which you need in order to correctly turn any cumulative counter in the same bin into a rate rather than treating it as a mystery running total; and this sits in the currently active extended Tx/Rx interval bin — its sibling StartTime/ClearTime fields mark exactly which window is being counted, so a change here reflects activity happening in the live collection interval, not something already filed away in history. For example, this field holding a value like '2026-08-06,14:30:00.0' tells you precisely which wall-clock window the rest of this bin's counters cover.