Talk about plans, predictions, arrangements and events still to come.
Predictions and on-the-spot decisions — I think it will rain; I'll get it!
Plans already made and predictions based on what you see now.
A fixed arrangement with a time and place already set — I'm meeting her on Friday.
Timetables and fixed schedules — the train leaves at nine.
An action that will be in progress at a specific future time.
An action that will be finished before a specific point in the future.
Talking from a past viewpoint about what was still to come — she said she would call.
On the verge of happening, or officially expected to — we're about to leave; the flight is due to land.
How long something will have been going on by a point in the future.