This is a date-and-time value marking when the performance-monitoring counters for this OTUC3 signal were last reset to zero, defaulting to the epoch placeholder 0000-00-00T00:00:00.000Z until a clear has occurred. Knowing this timestamp lets an admin correctly interpret the accompanying error and second counters, since a recent clear means low counts reflect a short window rather than a healthy long one. For example, if a technician manually clears OTUC3 statistics after a maintenance window, this field updates so later reports don't wrongly attribute pre-maintenance errors to the new baseline.