Four timestamps frame every shipment: ETD and ETA are the estimates for departure and arrival, ATD and ATA the actuals. The spread between ETA and ATA is the honest measure of how predictable a lane is. A quoted ETA from a carrier's transit-time table is a promise made once; a predictive ETA is recalculated from truck telematics, vessel AIS positions, and port queue data every few hours.

The point of a better ETA is not precision for its own sake: it is earlier bad news. A planner who learns six days out that a vessel has slipped four days can expedite the critical fraction of the load, resequence production, and let the rest come by sea; the same news arriving on the due date forces a line stop. Reliable ETAs also feed lead time statistics, and lower variability there directly reduces the safety stock a buyer must carry.

One trap: port ETA is not door ETA. A vessel's arrival says nothing about when the container clears the terminal, and dwell time at congested ports can add a week. Mature teams consume carrier ETAs through track and trace feeds into a supply chain visibility layer and measure each carrier's ETA accuracy rather than taking it on faith.