"It was an April afternoon. And the warm breezes of approaching summer had sent everyone, including Grandfather, indoors".
The above sentences are from the story 'Adventures in a Banyan Tree' by the Indian English writer Ruskin Bond. (The context of the story is a school boy's summer vacation excitements and experiences, which he narrates after the vacation. The summer vacation falls in April and May)
Based on these sentences, a question for editing came in an examination. But in the question, they used only "April" instead of "April afternoon" as shown below:
"It was (a) at April. The warm breeze of the approaching summer (b) have sent everyone indoors including grandfather".
Now my question is about the answer to (a): can it be an as in the actual sentence in the story?
Should it be in, the preposition before the name of a month?
[This question I asked on ELL a little while ago and I got an answer there. But the answer does not clear my doubt whether I can use in or not, as in It was in April.]
If the sentence were something like It was in April (a strange thing happened.), wouldn't it grammatically be an acceptable sentence?