This field reports collection start time of the bin, exposed here as cienaCesPmBasicTxRxCurrBinStartTime. 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 is in the currently open bin of that same basic bandwidth-profile-aware PM group — it keeps accumulating until its Duration elapses and it rolls into history, so reading it mid-interval gives you a partial, still-growing count. 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.