Departure time, STD is always off block time as per the ATC filing. Then there are some airports that publish TSAT and TOBT from there. Eurocontrol normally has a standard taxi time for each airport normally 10-20 minutes, but regardless of that the EET always starts at takeoff. Eurocontrol will see both actual OBT and TOT.
Some flight plan systems assume a certain standard taxi time to estimate the ETA from the STD and even the ETA at the alternate airport for info only, but I fail to see why you would need that as it rarely will be accurate.