If your flight leaves at 12:30, do you walk up to the gate a few seconds before that and expect to get on?
Is there anything with a departure time where you expect to be able to get on momentarily before departure?
Is there anything with a departure time where you expect to be able to get on momentarily before departure?
Things I walk up to momentarily before departure: every mode of transportation except planes. For trains and buses, the two times should be almost simultaneous (as anything else is just adding additional linger time)
The time given should ideally be when check-in closes - much easier to plan around.
There's arrival and departure (to the gate, platform, or quay) of the vehicle / vessel itself.
There's ticketing and check-in time, if those are required. Possibly security screening for air travel. And for aircraft, gate arrival time vs. wheels-down / wheels-up, where the latter includes taxi and takeoff queue time. Add to this the reliability or unreliability of actual travel times --- busses and shared-route transit must deal with traffic and delays, aircraft with weather and airport conjestion, ships with dock and pilot availability as well as weather factors, for example.
Schedules are written from several points of view --- the operator (when must vehicles be at specific points or departing from them), passengers, port or terminal operators, etc. Each has different needs. Learning how to interpret the published schedule to your own planning is key to effective use of such systems.
When the doors open, depending on traffic, they easily spend less than 20 seconds open before closing. I've run for a tube and dove in just in time _so_ many times now.