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  1. If I had gone to the party yesterday, I would be very tired today.

  2. If I had gone to the party yesterday, I would have been very tired today.

Witch one is correct? 1 or 2?

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  • 2 = correct. Search for info on the third conditional, which refers exclusively to the outcome of imaginary past events, rather than present facts or the imaginary future. Commented Jun 15, 2020 at 10:39
  • I disagree. So far as I'm concerned they're both syntactically and idiomatically valid, BUT if spoken during the afternoon, only the Perfect version (#2) would be valid with, for example, If I had gone to the party yesterday, I would have been very tired this morning. Commented Jun 15, 2020 at 12:49
  • See also Tense agreement in the past irrealis conditionals. Specifically the top answer there, citing Michael Swan's Practical English Usage (the "gold standard" in such matters, imho)... We sometimes use structures with would have ... to talk about present and future situations which are no longer possible because of the way things have turned out. Commented Jun 15, 2020 at 13:18

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