Japanese Language Stack Exchange is a question and answer site for students, teachers, and linguists wanting to discuss the finer points of the Japanese language. It only takes a minute to sign up.
Sign up to join this community
I'm struggling to understand how I can change the tense of conditional sentences.
For example, if I want to say "If I were him, I wouldn't say such things" I presume I would say "もし私が彼だったらあんなことは言わない". But if I want to say "If I were him, I wouldn't have said such things" should I say "もし私が彼だったらあんなことは言わなかった" ?
「あんなことは言{い}わなかった」 would be quite acceptable in non-formal speech. It would easily be understood to mean "I would not have said ~~" by native speakers if used in the right context.
You should, however, be at least aware that grammatically speaking, 「言わなかった」 is only in the simple past tense.
More formally and/or academically, you can say:
「言わなかったであろう」 and its shorter version is:
「言わなかっただろう」
It is also very natural and common to say:
「言わなかったと思{おも}う/思います」
Based on my understanding (JLPT N2), your suggested sentence "もし私が彼だったらあんなことは言わなかった" is correct.
Although in this case, I would agree with the comment on your OP above (which seems to no longer be there, maybe it was deleted) to use なら instead, unless there's a particular reason you want to use たら.
