MQTT Historians Need Source Event Time, Not Arrival Time
Global – October 29, 2026 -- Historians that stamp MQTT messages with broker arrival time can display an old pressure reading as a new process condition, distorting aggregates, alarms and event order during outage replays.
Plain MQTT defines no process-time field
MQTT specifies only the transport of an application message. It prescribes no timestamp field, industrial clock model or time semantics. The publisher's application contract decides whether a payload carries a time, in what format and with what quality.
OPC UA's SourceTimestamp and ServerTimestamp concepts do not carry over to ordinary MQTT payloads. Broker receipt time and connector receipt time are useful operational observations, but they do not prove when a machine produced a measurement.