1. He will be happy.

2. He will have been happy yesterday.
3. He would have been happy yesterday.
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Are they all grammatical?
Is #2 correct? What is the difference between #2 and #3? Does #2 have stronger possibility than #3? Does #3 mean that he was not happy actually.

1 answer

1 and 3 are fine. They don't mean the same thing, but they are written well.

2 makes no sense because "will have been" is future perfect, but then "yesterday" throws the meaning into past tense.