ATD
Ocean freightActual Time of Departure
The confirmed date and time the vessel or flight actually left.
In practice
Once the ATD is known the B/L can be dated and released, and the ETA is recalculated. Track-and-trace systems switch from ETD to ATD when the terminal reports the vessel sailed.
Seen in the wild
ATD confirmed 19 Oct 0230. B/L released.