This field reports collection start time of the bin, exposed here as cienaCesPmBasicTxRxHistoryBinStartTime. 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 lives in the basic bandwidth-profile-aware PM group's history bin — a closed-out interval whose own Duration and State tell you how long it ran and whether it closed cleanly, so the number is settled rather than still being written to. 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.