English uses various present forms to express future meaning, especially for formal scheduled events, imminent actions, and planned arrangements. These structures are more formal or specific than 'will' or 'going to'.
Quick tip: BE TO = formal scheduled. BE ABOUT TO = very soon/imminent. BE DUE TO = expected/scheduled time. BE SET TO = planned/expected.
BE TO + Infinitive (Formal Scheduled Events)
Use be to + infinitive for formal, official, or scheduled future events. Often used in news, announcements, and formal contexts.
The conference is to begin at 9am. (formal scheduled event)
The president is to visit next week. (official plan)
The meeting is to be held in Room 5. (scheduled arrangement)
You are to report to the manager immediately. (formal instruction)
Be About To + Infinitive (Imminent Action)
Use be about to + infinitive for actions that will happen very soon, almost immediately. Emphasizes that something is on the point of happening.
We are about to leave. (leaving very soon, almost now)
The train is about to depart. (departing imminently)
I was about to call you when you called me. (was on the point of calling)
Don't go - the show is about to start. (starting very soon)
Be Due To + Infinitive (Expected/Scheduled)
Use be due to + infinitive for things that are expected or scheduled to happen at a specific time, especially for transport, deadlines, or timetabled events.
The train is due to arrive in 5 minutes. (scheduled to arrive)
The report is due to be published next month. (expected publication)
She is due to graduate in June. (scheduled graduation)
The payment is due to be made on Friday. (expected deadline)
Common mistakes
Not "The meeting will to start at 3pm." — say "The meeting is to start at 3pm.". Use be to (not 'will to') for formal scheduled events. Pattern: is/are to + infinitive..
Not "We are about leave now." — say "We are about to leave now.". Always use 'to' after 'about': be about to + infinitive. Don't omit 'to'..
Practise it
Formal/official = BE TO. Very soon = BE ABOUT TO. Scheduled time = BE DUE TO. Planned/expected = BE SET TO.