futurepresent-tenseprogressive-aspectwill-be-goingwriting-style
From the grammatical point of view all are correct, just the meaning are different, please bring your clarification, thank you.
- The Train will leave at 10:00 tomorrow morning.
- The Train is going to leave at 10:00 tomorrow morning.
- The Train leaves at 10:00 tomorrow morning.
- The Train is leaving at 10:00 tomorrow morning.
Using will (or shall) is the proper way to form the actual future tense, and is completely generic. IT can be used in any case in which you wish to refer to the future.
Going to + verb is a shortcut construct that is commonly used in many situations. It is typically used to express occurrences in the near-future.
In many cases however, particularly in colloquial speech, the two constructs are virtually interchangeable.
Wikipedia has some additional notes on usage:
Going-to future is used when the speaker wishes to express certainty about the future based on evidence or fact from the present or the speaker's opinion: "If you do not stop, you are going to be caught by the police and hauled back to jail." "Our houses are going to be swept away by the impending storm." While the "will" and "going to" constructions are often interchangeable, only the "going to" construction can denote former future intention (e.g. "I was going to eat dinner, but decided not to").
They are all grammatical. Merriam-Webster gives three definitions of graduate in connection with schools.
transitive verb:
1 a : to grant an academic degree or diploma to
1 b : to be graduated from
intransitive verb:
1 : to receive an academic degree or diploma
If you are talking about a single student, the intransitive verb—"He will graduate in May" or "He is going to graduate in May"—is what is generally used.
Your second sentence: "He will be graduated in May," is the passive of *"X University will graduate him in May," using definition 1a (transitive). This sentence sounds strange to me because people usually use the intransitive in the active voice rather than the transitive in the passive voice (unless they have a good reason to use the transitive). However, "X University will be graduating 5,000 students in May" sounds perfectly fine. And you can come up with situations where the transitive in passive voice sounds fine with a single student, for example, "We will not be graduating Bob this year, but Ray will be graduated in May."
Definition 1b (transitive) appears in constructions like "I graduated MIT in 2009." This construction sounds informal to me, possibly because it become popular only after I learned English. I don't see any reason not to use "from MIT".
Google Ngrams shows that the transitive (1a) in passive voice was commonly formerly used for this, but is now rare, and that the popularity of (1b) is growing. However, the intransitive is generally what is currently used.
I am not going to go into the difference between going to and will in this answer; this difference has been hashed out several times on EL&U. For this sentence, both constructions are fine. The likelihood of graduation is the same for both constructions, and I consider them both acceptable in formal letters.
Best Answer
They're all just stylistic choices, with no difference in nuance of meaning.
The only context where "regular, repeat event" comes into play is when you say something like "The London train leaves at 8 o'clock" - if you don't specify any particular day, the implication is it does so every day (or at least, every week-day - it may leave at a different time, or not at all, on Saturday and/or Sunday).