I can help with that. Where would you be departing from?
I am looking for a train to Cambridge on Friday I am departing from Ely and I need it to arrive by 20:30.
{"__type": "Request", "service": "train", "values": ["departure"]}
{"__type": "Inform", "entity": {"__type": "Train", "arrive by": "20:30", "destination": "Cambridge", "trainid": "TR3492"}}
The TR3492 arrives in Cambridge at 19:52. That's the last train before 20:30.