inceptive future

Definition - A tense that indicates the future commencement of an action.

Example -

(1) I am going to eat.
(2) They are about to leave.

Oxford English Dictionary -
The term's first citation is from 1824:
"‘I am going to write’; ‘I am about to write’. These have been called the Inceptive future, as they note the commencement of an action."
(L. Murray Eng. Gram. (ed. 5) I. 128,)

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